INTEGRITY OF P/M FORGED Ni-Mo STEELS DETERMINED BY FRACTURE TOUGHNESS.

Plane strain fracture toughness tests of powder forged Ni-Mo steels in the quenched and tempered condition were used to determine the influence of process variables on properties. The effects of preform variables (powder type, size, density, sintering temperature), and forging variables (energy, temperature, rate) on K//I//c properties were studied and the results were used to suggest a modified powder forging route for improved properties. Scanning and transmission electron microscopy and optical metallography were used to correlate variations in K//I//c to structural features within the forgings. The results indicated a strong independence of K//I//c values on total oxygen level.