Spark plasma sintering cobalt base superalloy strengthened by Y–Cr–O compound through high-energy milling

Powder cobalt base superalloy prepared by high-energy balling and spark plasma sintering are studied through metallography and compression test. The experimental results shows that the powder size and crystalline grain decrease and distortions of crystal lattice increases with milling time. These trends slow down after milling for 8 h. Addition of 1.5% methanol can lessen powders adherence and agglomeration. The relative density of the sintered compact is 99.2% by spark plasma sintering at 1100 °C and 40 MPa. Its microstructure is fine with average grain size below 5 μm. Its compression strength and elongation are 2506 MPa and 2.5%. Annealing heat treatment at 1300 °C can improve its elongation but decrease its strength. They are 23.0% and 1982 MPa, respectively. The added nano-particles Y2O3 are changed into Y–Cr–O compounds to strengthen the cobalt base superalloy.