Fabrication of gas atomized Co-Cr-Mo alloy powder and microstructure of the hot-pressed compacts

Co-29Cr-6Mo alloy powder was fabricated by the gas atomizing process on the compacts were hot pressed at 1273 K to 1465 K with an applied pressure of 40 MPa for 7.2 ks. The atomized alloy powder possesses relatively small concentration scattering of chromium and molybdenum. The powder dominantly consists of fcc phase. The compacts hot pressed at 1273 K possess the relative density of 92%, meanwhile the compacts with high relative density (>98%) are obtained by sintering above 1323 K. The grain size of the compacts tends to increase with increasing sintering temperature. The σ phase in the fee matrix are observed in the compacts hot-pressed at 1273 K and 1323 K. Twins and stacking fault are observed and the σ phase disappear in the compacts hot-pressed over 1323 K. The compact hot-pressed at 1323 K shows the highest hardness value (374 Hv), resulting from the existence of the σ phase in the compact.