The effect of TiN coating on erosion–corrosion resistance of α-Ti alloy in saline slurry

Abstract

The slurry erosion–corrosion behaviour of TiN coated α-Ti alloy in aqueous silica slurry containing 3.5% NaCl has been investigated using a jet-in-slit rig. Erosion–corrosion tests were performed with slurry having jet velocity range 4.8–12.8 m s −1 and at normal impact angle. Because of synergistic effects between erosive wear and flow-induced corrosion, the erosion–corrosion rates of the TiN coating and α-Ti substrate were higher than the sum of erosive wear rates and flow-induced corrosion rates. At the lower slurry velocity, the TiN coating deposited on the α-Ti substrate presented better slurry erosion–corrosion resistance. With increasing slurry velocity, however, perforating, cracking and fragmenting of the hard TiN coating occurred and the protection effect of the coating layer reduced with the erosion–corrosion duration. And then the volume loss of the α-Ti substrate was enhanced through cracking of flakes induced by stress and corrosion.