Microstructures and abrasive wear performance of PTAW deposited Ni–WC overlays using different Ni-alloy chemistries

Abstract

The microstructures and performance of Ni–WC (nickel–tungsten carbide) composite overlays deposited by plasma transferred arc welding are studied using a combination of microscopy, hardness, and wear testing. The Ni–WC overlays had microstructures consisting of γ-Ni dendrites, with interdendritic Ni-based eutectics, borides and carbides. Overlays which were produced with a low hardness Ni-alloy matrix contained a smaller fraction of interdendritic phases relative to the high hardness Ni-alloys.The dissolution of WC particles was observed following deposition of the MMCs, and this promoted the formation of secondary carbide phases. Ni-alloys with low carbon and low Cr content exhibited the least dissolution of WC. The Ni–WC overlays produced using these dilute alloys generally performed better in ASTM G65 wear tests. This was due to the increased fraction of retained WC phase, and the reduced fraction of brittle secondary carbide phases when the Ni-alloy contained no Cr.