Wear resistance of laser clad chromium carbide surface layers

Abstract

Mixed powders of raw materials were laser melted on to an iron substrate to investigate the application of M7C3 chromium carbide as a hardfacing alloy. The hardness and abrasive wear resistance of the carbide layers were measured, and the thermal expansion of the bulk carbide alloys with compositions which corresponded to the carbide layers was examined to assess the bonding characteristics with the substrate materials. The microstructure of the surface layer containing 40 wt-%Cr consists of M3C and M7C3 type carbides and graphite, and that containing 80 wt-%Cr has a two phase mixture of M7C3 and M3C2 carbides, while the carbide layer with 60 wt-%Cr has afine cellular microstructure of nearly single phase M7C3 carbide. The carbide layers containing more than 60 wt-%Cr showed excellent wear resistance in comparison with widely used wear resistant alloys, and a comparable coefficient of thermal expansion to the iron substrate, which endows the surface layers with superior bonding with the substrate.MST/2084