Hardmetals as thermal spray coatings

Hardmetals are widely applied both as bulk materials and as coatings prepared by thermal spray processes. With progress in thermal spray technology and improved properties, these coatings have gained ever increasing technical importance and market share. Advanced hardmetal coatings are predominantly produced by high velocity oxy-fuel (HVOF) spraying, which is one of the most important thermal spray processes. A short historical survey is presented of hardmetal coating preparation by thermal spray processes. Selected questions of hardmetal compositions for coatings, chemical and metallurgical processes during spraying, and some coating properties, such as oxidation resistance, are then discussed. Finally commonalities and differences between bulk and coating hardmetals are briefly outlined.