Wear of thermal spray deposited low carbon steel coatings on aluminum alloys

Sliding wear behavior of low carbon steel coatings deposited on 319 Al allo y substrates using a plasma transfer wire arc (PTWA) thermal spraying proce ss was studied. The coatings had a layered microstructure consisting of ste el splats and FeO veins (0.5-3.0 mum thick) between them. Wear tests were p erformed using a pin-on-disc type wear tester within a load range of 10-75 N and a sliding speed range of 0.2-2.5 m/s against tool steel pins in a dry air atmosphere (7-10% RH). The wear rates, frictional forces, and surface temperatures were measured as a function of the applied load and sliding sp eed. In constant load tests, the wear rates decreased with increasing slidi ng velocity. The worn surfaces and the wear debris were characterized with optical microscopy (OM), scanning electron microscopy (SEM), energy dispers ive spectroscopy (EDS), X-ray diffraction (XRD), and microhardness. It was found that the wear rates and mechanisms could be divided between four load ing and velocity conditions. At low load and velocity, oxidation (formation of Fe2O3) was the main wear mechanism. The highest wear rates were associa ted with severe deformation of the steel splat tips and eventually splat fr acture and fragmentation and also formation of a mixture of iron oxides tha t occurred at low velocities and high loads. At high loads and velocities t he wear rates decreased, this was associated with the formation of thick pr otective oxide film and hardening of the sliding surface. (C) 2001 Elsevier Science BN. All rights reserved.