Wear Behavior And Wear Mechanism Of Hot-dip-Aluminized Coating On The Titanium Alloy

In this paper,titanium-aluminum intermetallic compound coating was prepared on TC4 alloy by hot-dip aluminizing and subsequently vacuum diffusion treatment with different temperature and time.Hot-dip-aluminized TC4 alloy treated for the650?and 0.5h diffusion annealing were performed on MPX-2000 wear tester by dry sliding wear tests under various velocities and loads,the wear behavior of the coating were studied systematically.The composition and structure of titanium-aluminum coating and the Phase,morphology,composition and performance of the worn surface and subsurface were studied by means of XRD,SEM,EDS,XPS and microhardness tester,and the formation and function of the tribo-layers during the wear process were analyzed emphatically,and wear mechanism of the coating was also discussed.The results show that the phase of the hot-dip-aluminized coating was TiAl₃intermetallic compound coating after being treated with different temperature and time diffusion.Diffusion temperature and time had an effect on the tissue and structure of the coating.It was found that the titanium-aluminum coating obtained by the aluminized layer after 0.5h diffusion was compact,and the interface was good with the matrix interface,and the hardness was as high as 614HV.With the increase of diffusion time and temperature,there are a lot of cracks and holes in the aluminized coating,even peeling.Thus,the quality of titanium-aluminium intermetallic compound coating after 650?diffusion for 0.5 h was best.It was found that the wear loss of titanium-aluminium intermetallic compound coating presented almost similar changes with the sliding velocity increased.In the sliding velocity of 0.5-4 m/s,the wear loss decreased with an increase of sliding velocity.After 0.75 m/s,the wear loss increased slowly,then rose sharply,and the wear loss reached the maximum value when the velocity is 2.68m/s.As the velocity increased continuously,the wear loss began to drop,and the wear loss decreased to the lowest value at 4m/s.Under the same sliding condition,the wear resistance of titanium-aluminum coating was the best at high velocity of 4m/s,while the wear resistance was the worst at 2.68m/s.Under the same sliding condition,the wear loss of TC4 alloy was significantly higher than that of titanium-aluminum intermetallic compound coating,especially at 4m/s.It can be seen that the wear resistance of TC4alloy was improved by titanium-aluminum intermetallic compound coating after the diffusion of aluminized titanium alloy.Through analysis,it can be concluded that this is mainly due to the joint action of titanium-aluminum coating and tribo-layers.The wear resistance of the TC4 alloy was improved by its own consumption or presence during the sliding process.Under different sliding conditions,the surface of the coating all formed a tribo-layer that was different from the based material.It was found that the wear resistance of titanium-aluminum coating depended on the characteristics and properties oftribo-layers.However,the characteristics and properties of tribo-layers determined the wear mechanism of titanium-aluminum coating.At 0.75 m/s,the continuous and thicker tribo-layer containing a certain amount of oxide possessed high HV_outmost510 and increased?HV_outmost113,and this kind of stable and ceramic tribo-layers had certain protective effect,and it reduced the wear lossand the wear mechanisms of aluminized coating are mainly adhesive wear and oxidation wear;at 4 m/s,more continuous and dense tribo-layer containing a large number of tribo-oxides possessed more high HV_outmost772 and increased?HV_outmost68,and more stable and ceramic tribo-layers has a significant protective effect,and it reduced the wear loss,and the wear mechanism was mainly mild-oxidative wear;while at 2.68 m/s the Slightly thick,discontinuous and loose tribo-layer containing little oxides possessed low HV_outmost491 and decreased?HV_outmost101,and this unstable and metallic tribo-layers had no protection,and the wear loss was the highest,and the main wear mechanism were delamination wear.