Microstructures and sliding wear resistances of 0.2arbon steel coatings deposited by HVOF and PTWA thermal spray processes英文电子书.pdf

Thin Solid Films 420 –421 (2002) 338–344 Microstructures and sliding wear resistances of 0.2% carbon steel coatings deposited by HVOF and PTWA thermal spray processes A. Edrisy, A.T. Alpas* Department of Mechanical Automotive and Materials Engineering, University of Windsor, 410 Sunset Avenue, Windsor, Ont., Canada N9B 3P4 Abstract Microstructures, and sliding wear resistances of low carbon (0.2% C) steel coatings produced using a plasma transfer wire arc (PTWA) process, and a high velocity oxygen fuel (HVOF) thermal spray process were compared. The wire feed stock used for both coatings was low carbon steel with a nominal 1020 composition. Results are also presented for HVOF coatings that had a 2.5 at.% Al addition to the steel wire feed stock. All thermal spray coatings had a layered microstructure consisting of steel splats and oxide veins between them. Detailed microstructural analyses showed that important differences existed in the microstructures and local compositions of coatings. Wear tests were performed 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 mys against tool steel pin in a dry air atmosphere (10% RH). Severe deformation of the steel splat tips on the contact surface, and their fragmentation was responsible for high wear rates at low speeds and high loads. Wear rates of PTWA 1020 and HVOF 1020—2.5% Al coatings decreased with increasing the sliding speed. However, the wear rates of HVOF 1020 coatings increased considerably at high sliding speeds, and this was associated with formation of thick oxide layers on its sliding surfaces, which reached 10 mm at 75 N and 2 mys. The wear mechanisms responsible for the differences in the sliding wear behaviour of the coatings are discussed in terms of differences in the microstructures of the coatings