Microstructural study of (Co–Ni–Fe) based alloys

Three types of hardfacing alloys containing a mixture of Co, Ni and Fe and a constant amount of C, Cr, W, Al, and Si were elaborated. The microstructure characterisation was carried out using different techniques of observations and analyses. The solidification phases are the M7C3 and M6C carbides in a solid solution rich in basic elements (Co, Fe, Ni, Al and Si). The structural evolutions induced by the ageing treatment were studied. A strong increase of the hardness was obtained. No difference in the nature of the phases present in the three alloys was noticed. The matrix is an ordered AlFe3 type (DO3) compound. Numerous precipitates are pointed out. Submicron cuboid M23C6 carbides and elongated precipitates with the Co2Si type structure (C37) were identified.