Effect of particle size and heating rate in microwave sintering of 316L stainless steel

• Heating rate of 15 K/min seems to be optimum in microwave sintering of 316L.
• The use of − 45 micron 316L WA powders improves mechanical properties.
• Positioning of the sample in the microwave furnace is a key factor.
• Difficulty in controlling the atmosphere in microwave furnaces is a negative point.
• Using fine 316L powder reduces oxidation and porosity, yields better properties.

The work evaluates the effect of heating rate in microwave sintering, and the effect of particle size of 316L powders in microwave and conventional sintering processes. The powders of 316L stainless steel were compacted by uniaxial press at 700 MPa, and sintered at 1250 °C for 1 h by means of conventional sintering and microwave sintering. The sintering atmospheres were Ar/H2 95/5% for conventional sintering and Ar/H2 90/10% for microwave sintering. Mechanical properties were evaluated using tensile tests. The samples were characterized by optical microscopy and SEM. The porosity levels were determined using image analysis software. Microwave sintering yields fully recrystallized microstructure different from conventional sintering, however no difference in distribution and shape of pores was noticed. Heating rate in microwave sintering affects densification, tensile strength and elongation. Moreover, the use of fine powders improves physical and mechanical properties of the samples sintered by both methods.

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