Metal-matrix composite coatings by PTA surfacing

Metal-matrix composite (MMC) coatings are deposited onto ferrous and non-ferrous substrates by three conventional techniques, namely laser cladding, thermal spraying and plasma transferred-arc (PTA) surfacing. In this paper PTA surfacing technology is reviewed with reference to current surface modification applications. The main rationale behind this technology has been focussed towards enhancing the tribological properties of the substrate. Little effort has been directed to investigating the corrosion behaviour of these coatings. The methods used in surface modification are either metallic alloying or the deposition of a composite layer. The metallic-alloying process has gained wider acceptance than the latter technique. While ferrous and high-density materials are commonly treated, the surface treatment of low-density materials remains a research exercise.