Characterization of titanium alloy and boron carbide metal matrix composites (MMCS) for surface engineering applications
- Authors: Ogunlana, M.O.
- Date: 2016
- Subjects: Titanium alloys - Fatigue , Lasers - Industrial applications , Laser-induced breakdown spectroscopy , Pulsed laser deposition , Metal coating
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/212809 , uj:21030
- Description: Abstract: Surface engineering applications has brought titanium and its alloys into limelight in the manufacturing industries such as the aerospace, automobile, marine, food processing and chemical processing industry. Despite the growths experienced in the use of this material, Ti and its alloys are plagued with poor wear behaviour especially when in contact with other materials during application. This limitation of Ti-based components has led to a search for techniques and processes to modify, restructure and re-engineer such materials for extended lifespan and for reuse. Among various techniques for restoring and protecting the material is by the use of the laser metal deposition (LMD) technique otherwise called the laser cladding process. The LMD is a technique used to achieve a coating on components which allow the addition of reinforcing particles to improve the surface properties of titanium-based materials. These properties include hardness, wear amongst others. This research study involves the use of the LMD process to deposit composites coatings on titanium alloy (Ti6Al4V) substrate using Rofin Sinar 3.0 KW Ytterbium fibre laser system. The reinforcement titanium alloy (Ti6Al4V) and boron carbide (B4C) ceramic powder were employed to deposit Ti6Al4V-B4C composites coatings on Ti6Al4V substrate. The microstructural evaluation, geometrical analysis, porosity analysis, microhardness profiling and the wear characteristics of laser cladded composites were investigated. Samples from the as-deposited laser cladded composites were characterized using optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Both geometrical and porosity analyses were carried out to investigate the rate of dilution and defects such as porosity and cracks on the deposited composites coatings. Furthermore, performance characteristics were investigated using microhardness tester and CETRUMT-2 tribometer for the wear test analysis of the laser clad coatings of Ti6Al4V-B4C composites. This research work is also aimed to establish process parameters that will result in defect-free composite coatings. The microstructure of the Ti6Al4V-B4C composites revealed a pore and crack free clad when observed at laser power of 2200 W. The SEM analysis revealed that there is uniform distribution of the ceramic particles in the titanium matrix at higher laser power. The geometrical analysis of the samples revealed that the aspect ratio (AR) and the dilution (D) increases with an increase in the laser power. The results obtained further revealed the dilution of approximately between 34% and 46% with aspect ratio between 2.16 and 3.58 were the best in terms of defectology for the combined with acceptable geometrical characteristics. The EDS and the XRD results revealed that there is a relationship between intermetallic phase of α+β titanium alloy and boron carbide in which certain amount of peaks... , M.Ing. (Mechanical Engineering)
- Full Text:
- Authors: Ogunlana, M.O.
- Date: 2016
- Subjects: Titanium alloys - Fatigue , Lasers - Industrial applications , Laser-induced breakdown spectroscopy , Pulsed laser deposition , Metal coating
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/212809 , uj:21030
- Description: Abstract: Surface engineering applications has brought titanium and its alloys into limelight in the manufacturing industries such as the aerospace, automobile, marine, food processing and chemical processing industry. Despite the growths experienced in the use of this material, Ti and its alloys are plagued with poor wear behaviour especially when in contact with other materials during application. This limitation of Ti-based components has led to a search for techniques and processes to modify, restructure and re-engineer such materials for extended lifespan and for reuse. Among various techniques for restoring and protecting the material is by the use of the laser metal deposition (LMD) technique otherwise called the laser cladding process. The LMD is a technique used to achieve a coating on components which allow the addition of reinforcing particles to improve the surface properties of titanium-based materials. These properties include hardness, wear amongst others. This research study involves the use of the LMD process to deposit composites coatings on titanium alloy (Ti6Al4V) substrate using Rofin Sinar 3.0 KW Ytterbium fibre laser system. The reinforcement titanium alloy (Ti6Al4V) and boron carbide (B4C) ceramic powder were employed to deposit Ti6Al4V-B4C composites coatings on Ti6Al4V substrate. The microstructural evaluation, geometrical analysis, porosity analysis, microhardness profiling and the wear characteristics of laser cladded composites were investigated. Samples from the as-deposited laser cladded composites were characterized using optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Both geometrical and porosity analyses were carried out to investigate the rate of dilution and defects such as porosity and cracks on the deposited composites coatings. Furthermore, performance characteristics were investigated using microhardness tester and CETRUMT-2 tribometer for the wear test analysis of the laser clad coatings of Ti6Al4V-B4C composites. This research work is also aimed to establish process parameters that will result in defect-free composite coatings. The microstructure of the Ti6Al4V-B4C composites revealed a pore and crack free clad when observed at laser power of 2200 W. The SEM analysis revealed that there is uniform distribution of the ceramic particles in the titanium matrix at higher laser power. The geometrical analysis of the samples revealed that the aspect ratio (AR) and the dilution (D) increases with an increase in the laser power. The results obtained further revealed the dilution of approximately between 34% and 46% with aspect ratio between 2.16 and 3.58 were the best in terms of defectology for the combined with acceptable geometrical characteristics. The EDS and the XRD results revealed that there is a relationship between intermetallic phase of α+β titanium alloy and boron carbide in which certain amount of peaks... , M.Ing. (Mechanical Engineering)
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Fabrication and characterization of functionally graded titanium alloy with commercially pure titanium and titanium carbide deposited by laser metal deposition technique
- Authors: Mdlalo, X. M.
- Date: 2015
- Subjects: Titanium alloys - Fatigue , Lasers - Industrial applications , Pulsed laser deposition , Metal coating
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/225271 , uj:22748
- Description: Abstract: Titanium and Titanium –based alloys have been used for aerospace materials for many years. Recently, those alloys are now being increasingly utilised for automotive, industrial, chemical, energy industries and consumer applications because of its excellent tensile and fatigue strength, corrosion resistance and high toughness- to- mass ratio, temperature strength and Young modulus’s values. However, despite these numerous applications, their general usages are often restricted because of limitations in mechanical properties and poor anti-friction properties exhibited in selected service conditions. There are different rapid solidification methods that have been put forward by some authors to address these deficiencies. Laser Metal Deposition has the potential to offer all specific solutions to key engineering problems over the traditional metal-working techniques. However, the purpose of this research work focuses on the laser metal deposition of CpTi /TiC composites coatings on Ti6A14V as a substrate by the laser melting of CpTi and TiC elemental powder mixtures. The process parameters involved with the LMD method include the laser power, traverse speed, powder-flow rate, and gas-flow rates. The characterization was done using OM, SEM, EDS, microhardness and tensile testing. The laser power was varied between 800W to 1600 W, while all the other parameters were kept constant. The results show that as laser power increases, the average hardness and the strength values also increase continuously. The results revealed that the microhardness values increases from 383 HV0.1 for the substrate and they reach a peak as high as 460 HV0.1 for sample A3 and the lowest value of 364 HV0.1 for sample A2. The tensile test showed that the average UTS for the four samples were 1545.18 MPa while the YTS and the percentage elongation were 932.60 MPa and 67% respectively. The average grain size of the substrate materials was determined to being 44.4 μm. The highest average grain size for sample A4 and lowest is for sample A1 of the deposited samples were found to be 79.8 μm and 67.7 μm respectively. , M.Ing. (Mechanical Engineering)
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- Authors: Mdlalo, X. M.
- Date: 2015
- Subjects: Titanium alloys - Fatigue , Lasers - Industrial applications , Pulsed laser deposition , Metal coating
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/225271 , uj:22748
- Description: Abstract: Titanium and Titanium –based alloys have been used for aerospace materials for many years. Recently, those alloys are now being increasingly utilised for automotive, industrial, chemical, energy industries and consumer applications because of its excellent tensile and fatigue strength, corrosion resistance and high toughness- to- mass ratio, temperature strength and Young modulus’s values. However, despite these numerous applications, their general usages are often restricted because of limitations in mechanical properties and poor anti-friction properties exhibited in selected service conditions. There are different rapid solidification methods that have been put forward by some authors to address these deficiencies. Laser Metal Deposition has the potential to offer all specific solutions to key engineering problems over the traditional metal-working techniques. However, the purpose of this research work focuses on the laser metal deposition of CpTi /TiC composites coatings on Ti6A14V as a substrate by the laser melting of CpTi and TiC elemental powder mixtures. The process parameters involved with the LMD method include the laser power, traverse speed, powder-flow rate, and gas-flow rates. The characterization was done using OM, SEM, EDS, microhardness and tensile testing. The laser power was varied between 800W to 1600 W, while all the other parameters were kept constant. The results show that as laser power increases, the average hardness and the strength values also increase continuously. The results revealed that the microhardness values increases from 383 HV0.1 for the substrate and they reach a peak as high as 460 HV0.1 for sample A3 and the lowest value of 364 HV0.1 for sample A2. The tensile test showed that the average UTS for the four samples were 1545.18 MPa while the YTS and the percentage elongation were 932.60 MPa and 67% respectively. The average grain size of the substrate materials was determined to being 44.4 μm. The highest average grain size for sample A4 and lowest is for sample A1 of the deposited samples were found to be 79.8 μm and 67.7 μm respectively. , M.Ing. (Mechanical Engineering)
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Characterization of laser metal deposited 17-4 PH stainless steel and tungsten composite for surface engineering applications
- Authors: Adeyemi, A.A.
- Date: 2018
- Subjects: Pulsed laser deposition , Metal coating , Metals - Mechanical properties , Lasers - Industrial applications , Stainless steel
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/284734 , uj:30767
- Description: Abstract: 17-4 PH Stainless steel is a martensitic characterized precipitation hardened stainless steel with excellent mechanical properties that has been tailored to industrial applications such as aerospace, automobile, marine, food processing equipment, oil and gas industries and chemical processing industries. Despite the growth experienced in the use of this material, 17-4 PH stainless steels are prone to degradation due to long service use in applications that required extreme hardness and wear resistance. This limitation led to the research of property enhancement of the material using modern fabrication technique called laser metal deposition additive manufacturing technology. Laser metal deposition is a modern additive manufacturing technique used in fabricating physical components from the configuration of a 3D CAD data model using a high intensity laser beam while depositing metallic powder on a substrate one layer at a time. This process is flexible in its use as it allows addition of reinforcing particles to improve surface properties of a metallic material such as hardness and wear amongst others. This research study presents the use of laser metal deposition process to investigate the property enhancement of 17-4 PH stainless steel through various characterization process such as microstructural evaluation, microhardness and wear test. The deposition process was carried out using Rofin Sinar Ytterbium fibre laser system of laser capacity of 3.0 kW. The reinforcement material was 17-4 PH stainless steel and tungsten metallic powder deposited on 316 stainless steel substrate. The deposition process commenced firstly with a trial-run deposition of 5 samples with multiple-track of 17-4 PH stainless steel at 50% overlapping percentage on 316 stainless steel substrate to establish process window. The reason for the trial-run was to achieve a deposition with no defects such as pores and cracks. After this was achieved, 17-4 PH stainless steel metallic powder and tungsten metallic powder were now deposited in form of multiple track at 50% overlapping percentage at high laser power and low laser power of 2600 W and 1500 W at varied tungsten powder flow rate on 316 stainless steel substrate. The microstructural evaluation, geometrical analysis, microhardness profiling and wear resistance characteristics of the deposited composites were investigated. The microstructural evolution investigation was carried out using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Geometrical analysis was carried out on the deposited composite samples both at high and low laser power to investigate the extent of laser... , M.Ing. (Mechanical Engineering)
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- Authors: Adeyemi, A.A.
- Date: 2018
- Subjects: Pulsed laser deposition , Metal coating , Metals - Mechanical properties , Lasers - Industrial applications , Stainless steel
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/284734 , uj:30767
- Description: Abstract: 17-4 PH Stainless steel is a martensitic characterized precipitation hardened stainless steel with excellent mechanical properties that has been tailored to industrial applications such as aerospace, automobile, marine, food processing equipment, oil and gas industries and chemical processing industries. Despite the growth experienced in the use of this material, 17-4 PH stainless steels are prone to degradation due to long service use in applications that required extreme hardness and wear resistance. This limitation led to the research of property enhancement of the material using modern fabrication technique called laser metal deposition additive manufacturing technology. Laser metal deposition is a modern additive manufacturing technique used in fabricating physical components from the configuration of a 3D CAD data model using a high intensity laser beam while depositing metallic powder on a substrate one layer at a time. This process is flexible in its use as it allows addition of reinforcing particles to improve surface properties of a metallic material such as hardness and wear amongst others. This research study presents the use of laser metal deposition process to investigate the property enhancement of 17-4 PH stainless steel through various characterization process such as microstructural evaluation, microhardness and wear test. The deposition process was carried out using Rofin Sinar Ytterbium fibre laser system of laser capacity of 3.0 kW. The reinforcement material was 17-4 PH stainless steel and tungsten metallic powder deposited on 316 stainless steel substrate. The deposition process commenced firstly with a trial-run deposition of 5 samples with multiple-track of 17-4 PH stainless steel at 50% overlapping percentage on 316 stainless steel substrate to establish process window. The reason for the trial-run was to achieve a deposition with no defects such as pores and cracks. After this was achieved, 17-4 PH stainless steel metallic powder and tungsten metallic powder were now deposited in form of multiple track at 50% overlapping percentage at high laser power and low laser power of 2600 W and 1500 W at varied tungsten powder flow rate on 316 stainless steel substrate. The microstructural evaluation, geometrical analysis, microhardness profiling and wear resistance characteristics of the deposited composites were investigated. The microstructural evolution investigation was carried out using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Geometrical analysis was carried out on the deposited composite samples both at high and low laser power to investigate the extent of laser... , M.Ing. (Mechanical Engineering)
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Fracture toughness characterisation of functionally graded grade 5 titanium alloy with titanium carbide
- Authors: Ratilal, Preyanka
- Date: 2016
- Subjects: Titanium alloys - Industrial applications , Titanium alloys - Fatigue , Lasers - Industrial applications , Metal coating
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213532 , uj:21165
- Description: Abstract: Functionally graded materials (FGMs) are composites consisting of two or more different materials with a gradient composition. These materials are drawing attention because they can provide new combined functions that surpass the characteristics specific to its constituent elements. The aim of this research is to determine the effect of processing parameters on the fracture toughness of laser processed Ti-6Al-4V (Grade 5) with Titanium Carbide (TiC) to form FGM. Other characterisation tests were also conducted, which include the microstructure and microhardness. Titanium alloys have been chosen as the study material in this research work because titanium and its alloys have a high production cost and are difficult to machine. As a result, titanium has a low industrial usage although it has superior mechanical properties when compared to steel. Literature study has revealed limited information on the properties and characteristics of functionally graded Ti6Al4V and TiC, particularly the fracture toughness behaviour. Preliminary design was carried out to obtain optimised laser processing parameters. A total of 13 trials were carried out by varying the laser power (0.6 kW – 2.5 kW), the scanning speed (0.045 – 3 mm/min), laser spot size (2 or 4 mm) and the power flow rate (3.34 g/min or 6.68 g/min). The specimens were then characterised with respect to the evolving microstructure and the microhardness. For certain processing parameters, cracking of the FGM deposit was observed and could be heard during processing. Optimized laser parameters were obtained for laser power between 1.5 kW to 2.5 kW and scanning speed between 2.5 m/min to 3 m/min. Functionally graded grade 5 titanium (Ti6Al4V) with titanium carbide (TiC) was successfully prepared by laser metal deposition (LMD). The TiC fraction was varied from 5 to 40 vol. % in increments of 5 percentage. A total of 8 layers were deposited to form the FGM. The laser power was varied from 1.5 kW to 2.5 kW in increments of 0.5 kW. A total of 3 laser power settings consisting of 5 specimens each were prepared for fracture toughness testing. The FGM specimens were cut using wire electical discharge machining (WEDM) to obtain a compact specimen design for fracture toughness. An alternative method to fatigue pre-cracking was used to produce the pre-crack. WEDM was used as an alternative due to it being less costly compared to fatigue pre-cracking. Also investigations have proven that the fracture toughness measurements were satisfied according to the ASTM E 399-90 ... , M.Ing. (Mechanical Engineering)
- Full Text:
- Authors: Ratilal, Preyanka
- Date: 2016
- Subjects: Titanium alloys - Industrial applications , Titanium alloys - Fatigue , Lasers - Industrial applications , Metal coating
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213532 , uj:21165
- Description: Abstract: Functionally graded materials (FGMs) are composites consisting of two or more different materials with a gradient composition. These materials are drawing attention because they can provide new combined functions that surpass the characteristics specific to its constituent elements. The aim of this research is to determine the effect of processing parameters on the fracture toughness of laser processed Ti-6Al-4V (Grade 5) with Titanium Carbide (TiC) to form FGM. Other characterisation tests were also conducted, which include the microstructure and microhardness. Titanium alloys have been chosen as the study material in this research work because titanium and its alloys have a high production cost and are difficult to machine. As a result, titanium has a low industrial usage although it has superior mechanical properties when compared to steel. Literature study has revealed limited information on the properties and characteristics of functionally graded Ti6Al4V and TiC, particularly the fracture toughness behaviour. Preliminary design was carried out to obtain optimised laser processing parameters. A total of 13 trials were carried out by varying the laser power (0.6 kW – 2.5 kW), the scanning speed (0.045 – 3 mm/min), laser spot size (2 or 4 mm) and the power flow rate (3.34 g/min or 6.68 g/min). The specimens were then characterised with respect to the evolving microstructure and the microhardness. For certain processing parameters, cracking of the FGM deposit was observed and could be heard during processing. Optimized laser parameters were obtained for laser power between 1.5 kW to 2.5 kW and scanning speed between 2.5 m/min to 3 m/min. Functionally graded grade 5 titanium (Ti6Al4V) with titanium carbide (TiC) was successfully prepared by laser metal deposition (LMD). The TiC fraction was varied from 5 to 40 vol. % in increments of 5 percentage. A total of 8 layers were deposited to form the FGM. The laser power was varied from 1.5 kW to 2.5 kW in increments of 0.5 kW. A total of 3 laser power settings consisting of 5 specimens each were prepared for fracture toughness testing. The FGM specimens were cut using wire electical discharge machining (WEDM) to obtain a compact specimen design for fracture toughness. An alternative method to fatigue pre-cracking was used to produce the pre-crack. WEDM was used as an alternative due to it being less costly compared to fatigue pre-cracking. Also investigations have proven that the fracture toughness measurements were satisfied according to the ASTM E 399-90 ... , M.Ing. (Mechanical Engineering)
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Stabilised C-band dual wavelength erbium doped fibre ring laser
- Authors: Mthukwane, Clarence Modise
- Date: 2018
- Subjects: Optical fibers , Lasers - Industrial applications , Optical amplifiers , Bragg gratings , Erbium
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280397 , uj:30130
- Description: M.Ing. (Electrical Engineering) , Abstract: In this dissertation, the realisation of a dual wavelength erbium doped fibre ring cavity laser configuration is discussed. The power stability and wavelength stability of a dual wavelength erbium doped fibre laser is investigated. The lasing wavelengths of the fibre laser are 1555.12 nm and 1560.32 nm. The laser is based on a ring cavity resonator which employs a 3 dB coupler and fibre Bragg gratings, as the wavelength selective component arrangement. The active medium in the cavity is a 3.2 m long erbium doped fibre with an absorption of 11.38 dB/m at 980 nm. To achieve simultaneous dual wavelength lasing with an erbium doped fibre laser configuration, there is one major challenge that must be overcome. The challenge is to correct the cavity losses on the selected wavelengths to achieve oscillation for all desired channels. In addition, because of the unevenness of the EDF gain profile, the threshold power for individual wavelengths is different. Subsequently, loss control across each of the selected wavelengths is required to balance the power difference between the wavelengths. The power and wavelength stability of the dual lasing wavelengths is investigated using an optical loop mirror with a 1 m length of single-mode fibre, and an unpumped erbium doped fibre of length 0.5 m, 1 m and 1.5 m. Also, the effect of changing the cavity length on the uniformity of the wavelength power increase relative to an increase in pump power together with the power and spectral stability of the lasing wavelengths is investigated. A 1m long Sagnac loop with a 70:30 coupling ratio was used to adjust the threshold power for simultaneous lasing of the two wavelengths. An increase in cavity length led to a good prospect for a stable dual wavelength laser with an output power difference of 0.4 dBm between the dual wavelengths and a power stability of 0.4 dB. The multi-wavelength and narrow spectral width of 0.19 nm and 0.20 nm of the laser can be used for dispersion measurement in wavelength division multiplexed communication links which consist of more than one wavelength. The laser was characterised for simultaneous dual wavelength output power response and power stability. The project presents the characterisation of an erbium doped fibre ring laser. The laser is cost effective and flexible in selecting preferred components for optimal performance in terms of power and wavelength stability, wavelength selectivity and narrow spectral width. Erbium doped fibre ring laser lasers are commercially available and are showing great promise in terms of their formidability and compatibility with current industrial requirements.
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- Authors: Mthukwane, Clarence Modise
- Date: 2018
- Subjects: Optical fibers , Lasers - Industrial applications , Optical amplifiers , Bragg gratings , Erbium
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280397 , uj:30130
- Description: M.Ing. (Electrical Engineering) , Abstract: In this dissertation, the realisation of a dual wavelength erbium doped fibre ring cavity laser configuration is discussed. The power stability and wavelength stability of a dual wavelength erbium doped fibre laser is investigated. The lasing wavelengths of the fibre laser are 1555.12 nm and 1560.32 nm. The laser is based on a ring cavity resonator which employs a 3 dB coupler and fibre Bragg gratings, as the wavelength selective component arrangement. The active medium in the cavity is a 3.2 m long erbium doped fibre with an absorption of 11.38 dB/m at 980 nm. To achieve simultaneous dual wavelength lasing with an erbium doped fibre laser configuration, there is one major challenge that must be overcome. The challenge is to correct the cavity losses on the selected wavelengths to achieve oscillation for all desired channels. In addition, because of the unevenness of the EDF gain profile, the threshold power for individual wavelengths is different. Subsequently, loss control across each of the selected wavelengths is required to balance the power difference between the wavelengths. The power and wavelength stability of the dual lasing wavelengths is investigated using an optical loop mirror with a 1 m length of single-mode fibre, and an unpumped erbium doped fibre of length 0.5 m, 1 m and 1.5 m. Also, the effect of changing the cavity length on the uniformity of the wavelength power increase relative to an increase in pump power together with the power and spectral stability of the lasing wavelengths is investigated. A 1m long Sagnac loop with a 70:30 coupling ratio was used to adjust the threshold power for simultaneous lasing of the two wavelengths. An increase in cavity length led to a good prospect for a stable dual wavelength laser with an output power difference of 0.4 dBm between the dual wavelengths and a power stability of 0.4 dB. The multi-wavelength and narrow spectral width of 0.19 nm and 0.20 nm of the laser can be used for dispersion measurement in wavelength division multiplexed communication links which consist of more than one wavelength. The laser was characterised for simultaneous dual wavelength output power response and power stability. The project presents the characterisation of an erbium doped fibre ring laser. The laser is cost effective and flexible in selecting preferred components for optimal performance in terms of power and wavelength stability, wavelength selectivity and narrow spectral width. Erbium doped fibre ring laser lasers are commercially available and are showing great promise in terms of their formidability and compatibility with current industrial requirements.
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Material characterization and analysis of laser cladding of titanium alloy
- Authors: Du Plooy, R.
- Date: 2018
- Subjects: Pulsed laser deposition , Lasers - Industrial applications , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269630 , uj:28645
- Description: M.Ing. (Mechanical Engineering) , Abstract: This study focused on laser cladding of Ti6Al4V, used as both the substrate and the powder material. The goal was to determine the most effective parameters for laser cladding, when using this alloy. The criteria used were both efficiency (i.e. how quickly a certain amount of area / volume could be cladded) and quality. To determine the most efficient and the highest quality cladding, the following was done: firstly, the samples were prepared by cladding multiple tracks, using varying scanning speeds for each track. The scanning speed was varied from 3.5m/min to 0.5m/min in increments of 0.5m/min; while the laser power, powder flow rate and gas flow rate was kept constant. Thereafter, a geometrical analysis, porosity analysis, microscopic analysis in the form of optical microscopy and scanning electron microscopy, atomic force microscopic analysis, Vickers microhardness testing and corrosion testing were all performed. One observation made from the optical and scanning electron microscopy was that the microstructure of the cladded area was consistent for sample scanning speeds ranging from 0.5m/min to 2.0m/min. This consistency also showed in the microhardness testing with the average hardness values for the scanning speeds ranging from 0.5m/min to 2.0m/min being almost equal at approximately 340HV. Corrosion resistance testing confirmed that the corrosion resistance of the clad was related to the scanning speed at which the clad tack was produced. In general it was shown that the slower the scanning speed the better the corrosion resistance. Further geometrical analysis of the micrographs obtained through optical microscopy revealed that sample five, with a scanning speed of 1.5m/min, yielded the best all-round clad, being the most efficient clad for the quality produced. The clads with higher scanning speeds, between 2.0m/min and 3.5m/min, could achieve area cladding rates greater than 50 000mm2/min; however the quality of the clad was not acceptable. The clads produced with slower scanning speeds (0.5 and 1.0m/min), did not produce a significant (or any) increase in the quality of the clad, when being compared with sample five. Overall this work proved successful; and it also yielded a number of ways whereby the current understanding and capabilities when considering the Laser Cladding of Titanium Alloys can be further improved.
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- Authors: Du Plooy, R.
- Date: 2018
- Subjects: Pulsed laser deposition , Lasers - Industrial applications , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269630 , uj:28645
- Description: M.Ing. (Mechanical Engineering) , Abstract: This study focused on laser cladding of Ti6Al4V, used as both the substrate and the powder material. The goal was to determine the most effective parameters for laser cladding, when using this alloy. The criteria used were both efficiency (i.e. how quickly a certain amount of area / volume could be cladded) and quality. To determine the most efficient and the highest quality cladding, the following was done: firstly, the samples were prepared by cladding multiple tracks, using varying scanning speeds for each track. The scanning speed was varied from 3.5m/min to 0.5m/min in increments of 0.5m/min; while the laser power, powder flow rate and gas flow rate was kept constant. Thereafter, a geometrical analysis, porosity analysis, microscopic analysis in the form of optical microscopy and scanning electron microscopy, atomic force microscopic analysis, Vickers microhardness testing and corrosion testing were all performed. One observation made from the optical and scanning electron microscopy was that the microstructure of the cladded area was consistent for sample scanning speeds ranging from 0.5m/min to 2.0m/min. This consistency also showed in the microhardness testing with the average hardness values for the scanning speeds ranging from 0.5m/min to 2.0m/min being almost equal at approximately 340HV. Corrosion resistance testing confirmed that the corrosion resistance of the clad was related to the scanning speed at which the clad tack was produced. In general it was shown that the slower the scanning speed the better the corrosion resistance. Further geometrical analysis of the micrographs obtained through optical microscopy revealed that sample five, with a scanning speed of 1.5m/min, yielded the best all-round clad, being the most efficient clad for the quality produced. The clads with higher scanning speeds, between 2.0m/min and 3.5m/min, could achieve area cladding rates greater than 50 000mm2/min; however the quality of the clad was not acceptable. The clads produced with slower scanning speeds (0.5 and 1.0m/min), did not produce a significant (or any) increase in the quality of the clad, when being compared with sample five. Overall this work proved successful; and it also yielded a number of ways whereby the current understanding and capabilities when considering the Laser Cladding of Titanium Alloys can be further improved.
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Experimental properties and simulated geometrical properties of Laser-metal-deposited Titanium
- Authors: Tayob, Mohammed Aqeel
- Date: 2016
- Subjects: Lasers - Industrial applications , Materials - Effect of radiation on , Titanium
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/82728 , uj:18994
- Description: Abstract: Laser metal deposition (LMD) is a manufacturing process, which can be used to manufacture a complete, fully functional part – by building it up layer-by-layer using the data from a Computer-Aided-Design (CAD) file. The layer-by-layer addition can also be used to rebuild worn-out sections of existing parts, as well as to deposit protective coatings to protect parts in surface engineering. The process involves laser heating a substrate, on which a metal powder is deposited. The powder solidifies, when mixed with the substrate, thereby creating a metallurgical bond. In order to produce parts with high geometrical tolerances and desirable material properties, the process parameters have to be carefully controlled. Since the LMD process requires the interaction of parameters, it is not always easy to predict the output geometry. In this dissertation, the laser-metal-deposition process was modelled in ANSYS Parametric-Design-Language (APDL), using a transient thermal analysis, in order to determine the geometrical properties of the clad, that is to say, the width and the height of the clad. The simulated results were then compared experimentally by depositing Commercially Pure (CP) titanium powder onto a Ti-6Al-4V substrate, in order to verify the simulation. The varying parameter in the experimental process was the powder-flow rate, which varied between 0.5-2.5g/min. In addition, to the geometrical properties, the microstructure, microhardness; and the porosity levels of the deposited clads were also analyzed, in order to better determine the clad quality and integrity. The model showed good agreement in predicting both the height and the width of the clads. Porosity was noticed in all the samples – with the exception of the clad deposited at the lowest powder-flow rate setting of 0.5 g/min. An increase in the powder-flow rate also led to a smaller fusion zone, due to a lower laser-material interaction period, which was the result of the increase in the quantity of powder causing attenuation of the beam, and less laser power being absorbed by the substrate. The smaller fusion zone meant that the clads could not bond to the substrate properly, which led to the clad in the sample with the highest powder-flow rate falling off the substrate. There was a significant increase in the microhardness of the clad zone, which was due to a combination of alloying with Ti-6Al-4V and a change in the microstructure to an acicular alpha martensite microstructure; while the Heat-Affected-Zone (HAZ) in the substrate only showed a slight increase in microhardness. , M.Ing. (Mechanical Engineering Science)
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- Authors: Tayob, Mohammed Aqeel
- Date: 2016
- Subjects: Lasers - Industrial applications , Materials - Effect of radiation on , Titanium
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/82728 , uj:18994
- Description: Abstract: Laser metal deposition (LMD) is a manufacturing process, which can be used to manufacture a complete, fully functional part – by building it up layer-by-layer using the data from a Computer-Aided-Design (CAD) file. The layer-by-layer addition can also be used to rebuild worn-out sections of existing parts, as well as to deposit protective coatings to protect parts in surface engineering. The process involves laser heating a substrate, on which a metal powder is deposited. The powder solidifies, when mixed with the substrate, thereby creating a metallurgical bond. In order to produce parts with high geometrical tolerances and desirable material properties, the process parameters have to be carefully controlled. Since the LMD process requires the interaction of parameters, it is not always easy to predict the output geometry. In this dissertation, the laser-metal-deposition process was modelled in ANSYS Parametric-Design-Language (APDL), using a transient thermal analysis, in order to determine the geometrical properties of the clad, that is to say, the width and the height of the clad. The simulated results were then compared experimentally by depositing Commercially Pure (CP) titanium powder onto a Ti-6Al-4V substrate, in order to verify the simulation. The varying parameter in the experimental process was the powder-flow rate, which varied between 0.5-2.5g/min. In addition, to the geometrical properties, the microstructure, microhardness; and the porosity levels of the deposited clads were also analyzed, in order to better determine the clad quality and integrity. The model showed good agreement in predicting both the height and the width of the clads. Porosity was noticed in all the samples – with the exception of the clad deposited at the lowest powder-flow rate setting of 0.5 g/min. An increase in the powder-flow rate also led to a smaller fusion zone, due to a lower laser-material interaction period, which was the result of the increase in the quantity of powder causing attenuation of the beam, and less laser power being absorbed by the substrate. The smaller fusion zone meant that the clads could not bond to the substrate properly, which led to the clad in the sample with the highest powder-flow rate falling off the substrate. There was a significant increase in the microhardness of the clad zone, which was due to a combination of alloying with Ti-6Al-4V and a change in the microstructure to an acicular alpha martensite microstructure; while the Heat-Affected-Zone (HAZ) in the substrate only showed a slight increase in microhardness. , M.Ing. (Mechanical Engineering Science)
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Characterising laser metal deposited titanium and molybdenum on titanium alloy for surface engineering applications
- Authors: Ntumba, Eric Muipatay
- Date: 2016
- Subjects: Laser-induced breakdown spectroscopy , Pulsed laser deposition , Lasers - Industrial applications , Titanium powder , Metal coating , Molybdenum
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/212802 , uj:21029
- Description: Abstract: In this work, sample study was done on the characterisation of Ti-10%Mo powder metal produced via LMD. Different process parameters were employed for the LMD process. The laser power was varied between 1kW and 2.2kW while keeping all other parameters constant. The scanning speed of 0.5m/sec, powder flow rate of pure titanium 1.8g/min and the powder flow rate of molybdenum 2g/min. were used for the coatings. The process parameters were carefully selected to represent low, medium and high settings. The characterisations carried out include optical microscopy and Scanning Electron Microscopy combined with Energy Dispersive Spectroscopy (SEM/EDS) techniques to investigate the particle distribution, microstructural evolution and chemical analysis of the welded samples. Vickers microhardness was used to determine the hardness distribution of the coating Ti6Al4V/Ti-Mo, the dry sliding wear tests were carried out on the deposited Ti6Al4V/Ti-Mo samples to determine the sliding wear of samples and corrosion tests was used to obtain information on the corrosion behavior of Ti6Al4V/Ti-Mo in 3.5% NaCl solution. The characterised laser metal deposited Ti6Al4V and Ti-Mo, revealed that the varied laser power played a main part in the microstructural evolution. It was found that the formation of the Widmanstӓtten structures improved the hardness of Ti6Al4V/Ti-Mo. The highest hardness value was found at the top zone of the clad owing to the presence of the reinforcement particles of Ti-Mo, the highest hardness value for all the samples was found at an average of 496HV. The sample produced at a laser power of 2kW and scanning speed of 0.5m/sec was found to show the lowest percentage of wear volume and the sample produced at laser power of 1.4kW and scanning speed of 0.5m/sec had the lowest percentage of the coefficient of friction; and this outcome can be attributed to the martensitic structure formed during cooling. The results obtained showed that the poor wear behaviour of the titanium alloy has been improved with the addition of Ti-Mo into their lattices. The experimental results indicated that the corrosion rate of the developed composites decreased significantly with the addition of the Ti-Mo powder. The results obtained from the polarization behavior show a decrease in the polarization resistance. While the open-circuit potential (OCP) for the alloy was found to reduce with time due to oxide film thickening on the metal surface... , M.Ing. (Mechanical Engineering Science)
- Full Text:
- Authors: Ntumba, Eric Muipatay
- Date: 2016
- Subjects: Laser-induced breakdown spectroscopy , Pulsed laser deposition , Lasers - Industrial applications , Titanium powder , Metal coating , Molybdenum
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/212802 , uj:21029
- Description: Abstract: In this work, sample study was done on the characterisation of Ti-10%Mo powder metal produced via LMD. Different process parameters were employed for the LMD process. The laser power was varied between 1kW and 2.2kW while keeping all other parameters constant. The scanning speed of 0.5m/sec, powder flow rate of pure titanium 1.8g/min and the powder flow rate of molybdenum 2g/min. were used for the coatings. The process parameters were carefully selected to represent low, medium and high settings. The characterisations carried out include optical microscopy and Scanning Electron Microscopy combined with Energy Dispersive Spectroscopy (SEM/EDS) techniques to investigate the particle distribution, microstructural evolution and chemical analysis of the welded samples. Vickers microhardness was used to determine the hardness distribution of the coating Ti6Al4V/Ti-Mo, the dry sliding wear tests were carried out on the deposited Ti6Al4V/Ti-Mo samples to determine the sliding wear of samples and corrosion tests was used to obtain information on the corrosion behavior of Ti6Al4V/Ti-Mo in 3.5% NaCl solution. The characterised laser metal deposited Ti6Al4V and Ti-Mo, revealed that the varied laser power played a main part in the microstructural evolution. It was found that the formation of the Widmanstӓtten structures improved the hardness of Ti6Al4V/Ti-Mo. The highest hardness value was found at the top zone of the clad owing to the presence of the reinforcement particles of Ti-Mo, the highest hardness value for all the samples was found at an average of 496HV. The sample produced at a laser power of 2kW and scanning speed of 0.5m/sec was found to show the lowest percentage of wear volume and the sample produced at laser power of 1.4kW and scanning speed of 0.5m/sec had the lowest percentage of the coefficient of friction; and this outcome can be attributed to the martensitic structure formed during cooling. The results obtained showed that the poor wear behaviour of the titanium alloy has been improved with the addition of Ti-Mo into their lattices. The experimental results indicated that the corrosion rate of the developed composites decreased significantly with the addition of the Ti-Mo powder. The results obtained from the polarization behavior show a decrease in the polarization resistance. While the open-circuit potential (OCP) for the alloy was found to reduce with time due to oxide film thickening on the metal surface... , M.Ing. (Mechanical Engineering Science)
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