vikas verma | Indian Institute Of Technology, Roorkee (original) (raw)
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The present work relates to the processing of dense alumina-based composites, their microstructur... more The present work relates to the processing of dense alumina-based composites, their microstructural characterization and study of mechanical properties. Alumina ceramic material and alumina-based composites with m-Zirconia and Ceria addition are sintered at 1600°C, 1650°C and 1700°C temperatures via conventional sintering. Solid-state diffusion during sintering led to volume diffusion in alumina, and volume and grain boundary diffusion in alumina composite. In the present sintering conditions alumina is found to be the least dense as improper solid-state diffusion resulted in porosity, whereas aluminazirconia composite achieved the highest density of 97%. Scanning electron microscope (SEM) micrograph shows homogeneous distribution of fine zirconia particles inside the alumina matrix, filling the voids of the alumina skeletal structure. Zirconia connects to alumina particles, restricting its abnormal grain growth. It results in strong bonding and grain refinement. Alumina-zirconia composite exhibits the highest hardness and fracture toughness of 14.37 GPa and 4.6 MPa · m 1/2 at 1700°C. Alumina suppresses the transformation of m-t zirconia, resulting in high toughness of alumina composites. Aluminazirconia-ceria composite revealed the presence of porosity, which led to less densification and low mechanical properties.
Four compositions of TiCN-WC-Ni/Co cermets with or without TaC were prepared by pressureless sint... more Four compositions of TiCN-WC-Ni/Co cermets with or without TaC were prepared by pressureless sintering of respective powders, and unlubricated sliding wear behavior against bearing grade steel ball was studied at 5, 10, or 20 N load. Maximum hardness and fracture toughness were obtained for Ti(CN)-5WC-10Ni-10Co-5TaC (in wt%) cermet. With change in the cermet composition and sliding load, coefficient of friction varied from 0.3 to 1.0 and wear rate varied from 3 9 10 À7 to 7 9 10 À7 mm 3 /Nm. The increased material transfer and formation of iron oxide-rich tribochemical layer were responsible for the reduction in friction and wear for Ti(CN)-5WC-10Ni-10Co-5TaC cermet.
The present work relates to the processing of dense alumina-based composites, their microstructur... more The present work relates to the processing of dense alumina-based composites, their microstructural characterization and study of mechanical properties. Alumina ceramic material and alumina-based composites with m-Zirconia and Ceria addition are sintered at 1600°C, 1650°C and 1700°C temperatures via conventional sintering. Solid-state diffusion during sintering led to volume diffusion in alumina, and volume and grain boundary diffusion in alumina composite. In the present sintering conditions alumina is found to be the least dense as improper solid-state diffusion resulted in porosity, whereas aluminazirconia composite achieved the highest density of 97%. Scanning electron microscope (SEM) micrograph shows homogeneous distribution of fine zirconia particles inside the alumina matrix, filling the voids of the alumina skeletal structure. Zirconia connects to alumina particles, restricting its abnormal grain growth. It results in strong bonding and grain refinement. Alumina-zirconia composite exhibits the highest hardness and fracture toughness of 14.37 GPa and 4.6 MPa · m 1/2 at 1700°C. Alumina suppresses the transformation of m-t zirconia, resulting in high toughness of alumina composites. Aluminazirconia-ceria composite revealed the presence of porosity, which led to less densification and low mechanical properties.
Four compositions of TiCN-WC-Ni/Co cermets with or without TaC were prepared by pressureless sint... more Four compositions of TiCN-WC-Ni/Co cermets with or without TaC were prepared by pressureless sintering of respective powders, and unlubricated sliding wear behavior against bearing grade steel ball was studied at 5, 10, or 20 N load. Maximum hardness and fracture toughness were obtained for Ti(CN)-5WC-10Ni-10Co-5TaC (in wt%) cermet. With change in the cermet composition and sliding load, coefficient of friction varied from 0.3 to 1.0 and wear rate varied from 3 9 10 À7 to 7 9 10 À7 mm 3 /Nm. The increased material transfer and formation of iron oxide-rich tribochemical layer were responsible for the reduction in friction and wear for Ti(CN)-5WC-10Ni-10Co-5TaC cermet.