Properties of WC–FeCrAl coatings manufactured by different high velocity thermal spray processes

Abstract

WC–FeCrAl coatings deposited by High Velocity Air-Fuel (HVAF) spraying and by High Velocity Oxygen-Fuel (HVOF) spraying with a liquid-fuelled and a gas-fuelled torch were studied and compared to a conventional HVOF-sprayed WC–CoCr coating.During HVOF spraying, WC–FeCrAl had a tendency to oxidise and decarburise. The gas-fuelled torch, operated with excess fuel, could restrain these phenomena, compared to the liquid fuelled one. In the HVAF coating, oxidation and decarburisation were further reduced, but porosity was >1%. As a consequence, the HVAF-sprayed coating was less hard than the HVOF-sprayed ones.Of all the WC–FeCrAl coatings, the gas fuelled-HVOF sprayed one exhibited the best wear resistance both in dry sliding conditions (at room temperature as well as at 400°C) and in dry particle abrasion testing. It indeed achieves the best compromise between density, hardness and low oxidation, so that it can reduce the extent of the brittle cracking phenomena affecting all WC–FeCrAl samples. Its dry sliding wear rate of ≈3∗10−8mm3/(Nm) at room temperature is even slightly lower than that of the WC–CoCr reference. Its performance under high temperature sliding and dry particle abrasion conditions is, however, somewhat poorer than that of the reference.