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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An evaluation of strain rate sensitivity of selected stainless steels at different temperatures
- Authors: Marques, Sérgio
- Date: 2012-09-12
- Subjects: Stainless steel , Metals - Mechanical properties , Strains and stresses
- Type: Thesis
- Identifier: uj:10242 , http://hdl.handle.net/10210/7613
- Description: M.Ing. , In the design and analysis of components and structures, detailed information on the material behaviour and its properties is required. When a material is loaded dynamically, such as in metal punching, the material properties may not be the same as when loaded statically. This is known as the strain rate sensitivity of a material, which implies that properties such as the yield strength, tensile strength and ductility may vary with the rate at which the material is loaded. South Africa is one of the large stainless steel producing countries. Seventy percent of the known chromium ore reserves are found in the Bushveld Igneous Complex in the Northern Province and Mpumalanga. To compete on the global stainless steel market it is essential that the South African producers have all the relevant product information directly available. Considerable research has been performed on mild steel at different strain rates and temperatures[1]. Work has also been done on some austenitic stainless steels. Very little, or no work has been done in this regard on ferritic and martensitic stainless steels and on the proprietary alloy 3CR12[2]. The aim of this thesis is to investigate the strain rate sensitivity of Types 304, 430 and 316 stainless steel, 3CR12 corrosion resistant steel and mild steel at different temperatures. To achieve this, tensile tests are performed. at strain rates between 10's -1 to approximately 100s -1 and at temperatures ranging from -40°C to 140°C. Shear tests are also performed at various strain rates, to investigate the effect that material behaviour has on a typical metal working process. The results obtained show that all the materials tested are strain rate sensitive. The strain rate sensitivity varies as a function of the material tested and the testing temperature. Constitutive models which take into account the strain rate sensitivity at room temperature for all the materials are also presented. These models describe the behaviour of the material fairly accurately. Three dimensional plots are also presented which depict how the yield strength, tensile strength and elongation vary as a function of both strain rate and temperature. These plots clearly show material trends for the strain rates and temperatures tested.
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- Authors: Marques, Sérgio
- Date: 2012-09-12
- Subjects: Stainless steel , Metals - Mechanical properties , Strains and stresses
- Type: Thesis
- Identifier: uj:10242 , http://hdl.handle.net/10210/7613
- Description: M.Ing. , In the design and analysis of components and structures, detailed information on the material behaviour and its properties is required. When a material is loaded dynamically, such as in metal punching, the material properties may not be the same as when loaded statically. This is known as the strain rate sensitivity of a material, which implies that properties such as the yield strength, tensile strength and ductility may vary with the rate at which the material is loaded. South Africa is one of the large stainless steel producing countries. Seventy percent of the known chromium ore reserves are found in the Bushveld Igneous Complex in the Northern Province and Mpumalanga. To compete on the global stainless steel market it is essential that the South African producers have all the relevant product information directly available. Considerable research has been performed on mild steel at different strain rates and temperatures[1]. Work has also been done on some austenitic stainless steels. Very little, or no work has been done in this regard on ferritic and martensitic stainless steels and on the proprietary alloy 3CR12[2]. The aim of this thesis is to investigate the strain rate sensitivity of Types 304, 430 and 316 stainless steel, 3CR12 corrosion resistant steel and mild steel at different temperatures. To achieve this, tensile tests are performed. at strain rates between 10's -1 to approximately 100s -1 and at temperatures ranging from -40°C to 140°C. Shear tests are also performed at various strain rates, to investigate the effect that material behaviour has on a typical metal working process. The results obtained show that all the materials tested are strain rate sensitive. The strain rate sensitivity varies as a function of the material tested and the testing temperature. Constitutive models which take into account the strain rate sensitivity at room temperature for all the materials are also presented. These models describe the behaviour of the material fairly accurately. Three dimensional plots are also presented which depict how the yield strength, tensile strength and elongation vary as a function of both strain rate and temperature. These plots clearly show material trends for the strain rates and temperatures tested.
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Development of TI6AL4V based metal matrix hybrid composites using laser metal deposition
- Authors: Ochonogor, Onyeka Franklin
- Date: 2018
- Subjects: Titanium-aluminum-vanadium alloys , Metallic composites , Metals - Mechanical properties
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/285978 , uj:30936
- Description: D.Phil. (Mechanical Engineering) , Abstract: Three alloy particles; Ti6Al4V alloy, Boron Nitride (BN) and Boron Carbide (B4C) particle were compacted and deposited to the surface of Ti6Al4V alloy substrate using laser metal deposition, an advance additive manufacturing laser technology system attached with three hopper feeders for powder delivery to form a hybrid metal matrix composite. The high demand for improved properties of Ti6Al4V alloy metal matrix composites has led to the fabrication of Ti6Al4V metal with good hardness and most importanly for wear application. Combined properties of Ti6Al4V alloy, Boron Nitride (BN) and Boron Carbide (B4C) particles with unique mechanical properties may result in enhancing the resistance to matrix cracking and the forming of a Ti6Al4V metal - matrix hybrid composite. The combination of three different reinforcement powder particles is often very difficult due to extreme hardness property that often affects the homogenization and bonding mechanism, yet such hybrid composites has a number of benefits in service. However, good combination of properties was possible with the aid of an Nd: YAG laser system attached with three hopper system that delivered powder particles into the melt pool created on the surface of the substrate. Boron carbide / nitride additions were less than 10 volume percent with Ti6Al4V alloy powder having more than 90 volume percent to enable grain growth control, which resulted in good metallurgical bonding in the composites. Double tracked Ti6Al4V - BN - B4C composites were fabricated at different laser power and composition / variations, which were used to form the basis for the experiments. Ten samples were fabricated using laser power ranging between 1700 W and 2800 W while the scanning speed was kept constant at 1.0 m/min. This project however focused on Ti6Al4V - BN - B4C powder coatings on titanium alloy substrate at different process parameters. Optimized samples were therefore cut to experimental sizes and the effect of laser power on the deposition process and powder flow rate were investigated. The resultant microstructures revealed an excellent and homogeneous distribution of the martensitic metal matrix composite structure (MMCs). The Ti6Al4V - BN - B4C composites were crack and pore free, with enabling phase transformation in the martensites. The optimized samples were selected for 2000 W and 1400 W due to good surface integrity, absence of porosity good metallurgical and mechanical properties such as fine grain structure with excellent bonding strength...
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- Authors: Ochonogor, Onyeka Franklin
- Date: 2018
- Subjects: Titanium-aluminum-vanadium alloys , Metallic composites , Metals - Mechanical properties
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/285978 , uj:30936
- Description: D.Phil. (Mechanical Engineering) , Abstract: Three alloy particles; Ti6Al4V alloy, Boron Nitride (BN) and Boron Carbide (B4C) particle were compacted and deposited to the surface of Ti6Al4V alloy substrate using laser metal deposition, an advance additive manufacturing laser technology system attached with three hopper feeders for powder delivery to form a hybrid metal matrix composite. The high demand for improved properties of Ti6Al4V alloy metal matrix composites has led to the fabrication of Ti6Al4V metal with good hardness and most importanly for wear application. Combined properties of Ti6Al4V alloy, Boron Nitride (BN) and Boron Carbide (B4C) particles with unique mechanical properties may result in enhancing the resistance to matrix cracking and the forming of a Ti6Al4V metal - matrix hybrid composite. The combination of three different reinforcement powder particles is often very difficult due to extreme hardness property that often affects the homogenization and bonding mechanism, yet such hybrid composites has a number of benefits in service. However, good combination of properties was possible with the aid of an Nd: YAG laser system attached with three hopper system that delivered powder particles into the melt pool created on the surface of the substrate. Boron carbide / nitride additions were less than 10 volume percent with Ti6Al4V alloy powder having more than 90 volume percent to enable grain growth control, which resulted in good metallurgical bonding in the composites. Double tracked Ti6Al4V - BN - B4C composites were fabricated at different laser power and composition / variations, which were used to form the basis for the experiments. Ten samples were fabricated using laser power ranging between 1700 W and 2800 W while the scanning speed was kept constant at 1.0 m/min. This project however focused on Ti6Al4V - BN - B4C powder coatings on titanium alloy substrate at different process parameters. Optimized samples were therefore cut to experimental sizes and the effect of laser power on the deposition process and powder flow rate were investigated. The resultant microstructures revealed an excellent and homogeneous distribution of the martensitic metal matrix composite structure (MMCs). The Ti6Al4V - BN - B4C composites were crack and pore free, with enabling phase transformation in the martensites. The optimized samples were selected for 2000 W and 1400 W due to good surface integrity, absence of porosity good metallurgical and mechanical properties such as fine grain structure with excellent bonding strength...
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Nanoindentation studies on titanium nitride nanoceramic reinforced titanium-aluminium-vanadium alloys
- Authors: Maja, Mosima Edith
- Date: 2018
- Subjects: Titanium-aluminum-vanadium alloys - Testing , Nanoelectronics , Metals - Mechanical properties , Nanoindentation
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/285986 , uj:30937
- Description: M.Tech. (Chemical Engineering) , Abstract: Recent development in nanoindentation techniques has enabled investigations on the mechanical properties of materials under dynamic conditions as the technique offers unique capabilities for direct measurement of hardness, modulus of elasticity and contact stiffness among other properties. In this study, ultra nanoindentation (UNHT) technique was used to investigate the mechanical properties of spark plasma sintered Ti-6Al-4V reinforced with 1 to 4 vol% TiN nanoparticles. The morphology and microstructure of the as-sintered samples were examined using field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS) and Electron Backscattered Diffraction (EBSD). The hardness, modulus of elasticity and creep properties were examined using Berkovich diamond indenter which is equipped with a three-sided pyramid. Microstructural results indicated that sintered samples containing 1 vol % of TiN nanoparticles was fully transformed from lamellar to bimodal and duplex structures. It was also observed that TiN nanoparticles segregated at the grain boundaries of the Ti-6Al-4V matrix. Results obtained from the EBSD revealed that α phase, hexagonal close packed (HCP) was stabilised at the expense of β phase Body centered cubic crystal structure (BCC). The nanoindentation results showed that both hardness and modulus of elasticity depend on the presence of volume fraction of TiN in Ti-6Al-4V matrix. There was significant increase in bulk hardness, modulus of elasticity while subsequently decreasing the contact depth and maximum depth of the indentation with increase in volume fraction of TiN. The mechanical properties (hardness and modulus of elasticity) of each phase (α and β) were derived from the grid indentation technique, where the β phase exhibited the highest hardness against α phase and the grain boundary, which may be due to uniform distribution of TiN along the grain boundary and β phases were found along the grain boundary. Optimum properties were obtained with the addition of 2 vol % of TiN which had highest creep resistance compared with that of Ti base alloy.
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- Authors: Maja, Mosima Edith
- Date: 2018
- Subjects: Titanium-aluminum-vanadium alloys - Testing , Nanoelectronics , Metals - Mechanical properties , Nanoindentation
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/285986 , uj:30937
- Description: M.Tech. (Chemical Engineering) , Abstract: Recent development in nanoindentation techniques has enabled investigations on the mechanical properties of materials under dynamic conditions as the technique offers unique capabilities for direct measurement of hardness, modulus of elasticity and contact stiffness among other properties. In this study, ultra nanoindentation (UNHT) technique was used to investigate the mechanical properties of spark plasma sintered Ti-6Al-4V reinforced with 1 to 4 vol% TiN nanoparticles. The morphology and microstructure of the as-sintered samples were examined using field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS) and Electron Backscattered Diffraction (EBSD). The hardness, modulus of elasticity and creep properties were examined using Berkovich diamond indenter which is equipped with a three-sided pyramid. Microstructural results indicated that sintered samples containing 1 vol % of TiN nanoparticles was fully transformed from lamellar to bimodal and duplex structures. It was also observed that TiN nanoparticles segregated at the grain boundaries of the Ti-6Al-4V matrix. Results obtained from the EBSD revealed that α phase, hexagonal close packed (HCP) was stabilised at the expense of β phase Body centered cubic crystal structure (BCC). The nanoindentation results showed that both hardness and modulus of elasticity depend on the presence of volume fraction of TiN in Ti-6Al-4V matrix. There was significant increase in bulk hardness, modulus of elasticity while subsequently decreasing the contact depth and maximum depth of the indentation with increase in volume fraction of TiN. The mechanical properties (hardness and modulus of elasticity) of each phase (α and β) were derived from the grid indentation technique, where the β phase exhibited the highest hardness against α phase and the grain boundary, which may be due to uniform distribution of TiN along the grain boundary and β phases were found along the grain boundary. Optimum properties were obtained with the addition of 2 vol % of TiN which had highest creep resistance compared with that of Ti base alloy.
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