Response to thermal treatment of a powder metallurgy Fe‐0.8 % B‐1.3 % C‐1.6 %Cr alloy

Argon atomized powders of the Fe‐0.8%B‐1.3%C‐1.6%Cr alloy in the rapid solidification condition as well as the consolidated material were characterized. Consolidation was carried out by extrusion at 1050°C and by hot isostatic pressing at 700°C. The microstructure of powder particles in the rapid solidification condition is dendritic and remains unchanged after hot isostatic pressing. This microstructure is gradually lost after annealing at temperatures above 900°C. The extruded material presents a fine and homogeneous microstructure constituted by small grains of laminar pearlite and spherical M 23 (B,C) 6 borocarbides of 1.8 μm in size. A martensite microstructure with a uniform dispersion of M 3 (B,C) borocementite particles is obtained after annealing at 1095°C 10 min and water quenching. For long austenitization time at 1095°C, a coalescence of borocementite as well as decarburization is observed in the steel. Dilatometric studies, between 20 and 400°C, of samples quenched from 1095°C show the presence of two contraction volume points at 160 and 310°C. At 160°C, the high carbon martensite decomposes into a two phase mixture of metastable carbides and low carbon martensite. At 310°C simultaneous transformation of austenite to ferrite and metastable carbides into cementite occurs.