M23C6 carbide dissolution mechanisms during heat treatment of ASTM f-75 implant alloys

The dissolution of M23C6 carbides in an ASTM F-75 alloy was experimentally followed, during a liquid-phase homogenization treatment, in as-cast and pr etreated for partial carbide dissolution (PTPCD) specimens. The results rev ealed that before the fusion of the carbides, solid-state diffusion of the elements forming the carbides occurred. After the fusion of the carbides, a serrated interface developed. Treatment periods longer than 1000 seconds l ed to a liquid-carbide zone morphology showing the presence of dendrites wi thin the liquid phase. Energy dispersion spectrometry (EDS) analysis reveal ed that the composition of such dendrites was very close to that of the alp ha -phase matrix. The observed microstructure features are explained in ter ms of a solutal diffusion-driven mechanism leading to the growth of the mat rix by consuming the liquid phase formed by the carbide fusion.