FRICTION SURFACING OF METAL COATINGS ON STEEL AND ALUMINUM SUBSTRATE

Friction surfacing of (i) tool steel, inconel, aluminum and titanium r ods onto mild steel substrates and (ii) stainless steel, mild steel an d inconel onto aluminum substrates was investigated. It was found that tool steel and inconel were efficiently deposited onto steel to form a dense strong coating while aluminum was only deposited at high conta ct pressures. Titanium could not be deposited under the tested conditi ons. Stainless steel, mild steel and inconel could be deposited onto a luminum substrates to form dense coatings, however only SS displayed a lack of intermetallic compound formation with Al. Melting of Al by fr ictional heat was observed and this led to the formation of brittle an d therefore undesirable intermetallic compounds at the interface of th e coating. X-ray microscope investigations of the coatings confirmed t hat the structure of the coating is a continuous series of discrete la yers inclined at a shallow angle to the phase of the substrate. Fissur es were found between these layers close to the outer surface of the c oating, which implies that the uppermost layers should be removed to o btain the best quality of coating. Microscopic observations revealed t hat there was little mixing between the coating and the steel substrat e but some surface roughening and sub-surface deformation of the steel substrate by friction surfacing. The Al-alloy substrate showed simila r types of surface alteration but to a far greater extent. Careful con trol of process parameters such as substrate, speed load and consumabl e was necessary for coating quality. (C) 1997 Elsevier Science S.A.