Microstructure and mechanical properties of microwave sintered austenitic stainless steel

The objective of this work is focused on understanding the effect of microwave heating on sintering of 316L powders. The stainless steel samples were prepared from prealloyed powders of 316L. The powder samples were compacted at a pressure of 560 MPa and sintered at 1300 degrees C in a microwave furnace of 2.4 GHz and 2KW capacity in nitrogen atmosphere. The sintering time was varied from 10 to 20 minutes in order to study the effect of sintering time on sintering behavior and mechanical properties of the sintered samples. The sintered samples were subjected to optical metallography, hardness testing, tensile testing and fractogrphy. The average density of sintered stainless steels was 92% of the theoretical density, approximately 18% increment from green density for 20 min. sintering time. Microstructural analysis showed the regularly distributed porosity with very small grains. The hardness value was in the range of 365VHN to 396VHN and tensile strength, in the range of 255MPa to 580 MPa. Fractographs for these steels revealed mixed mode of fracture.