A Low Cobalt Powder Metallurgy Superalloy

A POWDER METALLURGY DISC SUPERALLOY, LOW IN COBALT, BASED ON THE SOVIET CAST BLADE SUPERALLOY, ZHS6-K HAS BEEN PREPARED BY ARGON ATOMIZATION AND HOT ISOSTATIC PRESSING. CONSOLIDATION OF THE ALLOY AT A TEMPERATURE CLOSE TO ITS GAMMA PRIME SOLVUS PRODUCED A MICROSTRUCTURE FREE FROM PRIOR PARTICLE BOUNDARY PRECIPITATES. THE INTERGRANULAR CARBIDES WERE FOUND TO BE OF THE M(SUB 6)C TYPE. THE HEAT TREATMENT, 1080 C/8 H, RAPID AIR COOL + 650 C/24 H, AIR COOL + 760 C/16 H, AIR COOL, OFFERED THE BEST COMBINATION OF TENSILE AND STRESS RUPTURE PROPERTIES DUE TO FINELY DISTRIBUTED CARBIDE PRECIPITATES, COARSE GAMMA PRIME PRECIPITATES AT THE GRAIN BOUNDARIES AND A BIMODAL DISTRIBUTION OF INTRAGRANULAR GAMMA PRIME PARTICLES. ANOTHER HEAT TREATMENT, 1220 C/2 H, RAPID AIR COOL + 1050 C/8 H, AIR COOL + 850 C/16 H, AIR COOL, RESULTED IN THE FORMATION OF A CONTINUOUS CARBIDE NETWORK AT GRAIN BOUNDARIES AND A HIGH VOLUME FRACTION OF FINE GAMMA PRIME PARTICLES WITH A RAFT LIKE MORPHOLOGY. THIS HEAT TREATMENT RESULTED IN REDUCED ALLOY STRENGTH AT HIGH TEMPERATURES.