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)
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- 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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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)
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- 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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