Preparation and wear resistance of B–Al co-permeation layers on TC4 titanium alloy surface

Abstract

The surface of the TC4 titanium alloy was treated by B–Al co-permeation at 900, 1000, and 1100 °C for 4 h using the powder pack co-cementation method. The microstructure, elemental distribution, phase composition, hardness and wear resistance of the composite layers were analyzed by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, a microhardness tester, and a multifunctional surface mechanical property tester. The results showed that the phase composition of the layers obtained under different processes includes TiB, TiB2, Ti3Al, and Al2O3. The thickness of the coatings increases with the increase of temperature, ranging from 2.00 ± 0.14–8.67 ± 0.62 μm. The outer layers are composed of Al2O3 and Ti3Al, and the inner layers are TiB and TiB2. The hardness range of the composite layers is 1168.1–1939.8 HV0.1, which is nearly 3–5 times that of the substrate. The friction and wear experiment results showed that the average friction coefficient of the B–Al composite layer is lower than that of the matrix. The friction coefficient at 1000 ℃ is the smallest, which is 0.20. The volume wear rate of the composite layer is approximately 38–44% that of the matrix. The wear mechanism of the TC4 titanium alloy is abrasive and oxidative wear, while that of the B–Al co-deposition layer is abrasive, adhesive, and oxidative wear.