Slurry erosion characteristics of TiN coatings on α-Ti and plasma-nitrided Ti alloy substrates

Abstract

The slurry erosion behavior of TiN coatings on α-Ti and plasma-nitrided Ti alloy substrates in aqueous silica slurry has been investigated using a jet-in-slit rig. Erosion tests were performed with slurry jet velocities between 6.4 and 15.2 m s−1. At the lower slurry velocity, pitting was caused by the slurry impact, and there was little volume loss for each of the coatings. The TiN coatings deposited on the α-Ti and nitrided Ti alloy substrate presented high slurry erosion resistance. With increasing slurry velocity, however, perforation and fragmentation of the hard TiN coatings occurred and the protection effect of the coating layer reduced with the erosion duration. The erosion rates for the coatings deposited on the nitrided Ti substrate were slightly lower than those for the coatings deposited on the α-Ti substrate under the same test conditions. After coating perforation, the surfaces of the substrates were eroded by crater formation and flaking on the center section of the erosion scars while cutting and plowing occurred at the outer regions of the erosion scars.