Metal-matrix composite (MMC) coatings consisting of a nickel based metal matrix, providing toughness and tungsten carbides, providing wear resistance, are used in applications subjected to severe abrasive wear conditions. The aim of this work is to map the influence of type, morphology and amount of tungsten carbides in a nickel based matrix on the wear resistance and microstructure of laser cladded MMC coatings. Abrasive wear, evaluated according to ASTM-G65, is mainly influenced by the volume fraction of the tungsten carbides in the coating. Shape and microstructure of the tungsten carbides have a minor impact on this property, for similar degree of melting or dilution from the substrate material and size of the tungsten carbides. Microstructure analysis shows that the dissolution of the tungsten carbides in the melt pool is influenced by the chemical composition of the liquid metal phase, the microstructure and the amount of tungsten carbides selected.

HVOF and HVAF deposited coatings of three commercial Fe-based powder alloys have been ranked according to ASTM G76 solid particle erosion testing. The reference was electrolytic hard chrome (EHC) plating. The test results at 30 m/s abrasive particle velocity showed that 6AB powder alloy, when HVAF sprayed, Fe SP586 when both HVOF and HVAF sprayed meet the EHC plating reference erosion rate. 6AB HVOF sprayed and Fe SP529 both HVOF and HVAF sprayed powder alloys achieved two to three times higher erosion rate but were still at the same level of magnitude as the EHC plating reference.

This study ranks a number of common thermal surfacing materials for soil tillage applications based on the results of dry-sand rubber-wheel testing for abrasion resistance. Test specimens were prepared by plasma transferred arc (PTA) and powder welding deposition of a nickel-based self-fluxing matrix with and without tungsten carbide (WC) additions. For comparison, PTA coated M2 tool steel and quenched and tempered spring steels were also tested. PTA and PW deposition produced coatings with a similar level of abrasive wear resistance. Hardfacing with M2 and nickel-based 1560 deposited by PTA showed ~30% and ~15% wear respectively compared to the reference steels, while nickel-based grades with additions of 50% carbide showed only ~5% wear. Moreover, by increasing the amount of WC from 50 to 60 wt%, abrasive wear resistance was increased by 25%.