Research On The Fretting Wear Properties Of CuNiAl Alloys With Ti₃SiC₂ Coatings

Nickel-aluminum bronze are extensively used in the critical component of marine equipment,for instance,the hub and valve.In the blade bearings of a controllable pitch propeller,which are formed by the blade carrier together with the blade foot and the hub,fretting wear is easily caused in a relatively poor marine environment and it is the leading factors affecting the service life of the controllable pitch propeller.Therefore,it is necessary to carry out a research on the fretting wear properties as well as failure mechanisms of CuNiAl alloys and find suitable approaches to improving its wear resistance.By plasma spraying wear-resistant Ti₃SiC₂ coatings on the surface of CuNiAl alloys,torsional fretting wear experiments are performed under the flat-on-flat contact configuration.Fretting wear properties as well as wear mechanisms of CuNiAl alloys and Ti₃SiC₂ coatings are investigated comparatively.The improvement of plasma powers and the pre-oxidation thermal treatment are discussed for an elevated wear properties under fretting condition.The main conclusions obtained from the present work are as follows:?1?Fretting wear properties of CuNiAl alloys and Ti₃SiC₂ coatings are investigated at different normal loads?43N,86N,106N?and different angular displacements?0.1°,0.5°,1.5°,3°?.The results shows that fretting running regimes of CuNiAl alloys change from partial slip regime to gross slip regime with the increase of the angular displacement amplitudes,corresponding to the decrease of the friction coefficients and the increasingly severe wear damage.While Ti₃SiC₂ coatings run in the slip regime except for the angular displacement of 0.1°.The wear resistance has been improved by one or two orders of magnitude and the friction coefficient exhibits a decrease compared to Ti₃SiC₂ bulks at the same time.?2?Further improvement of wear properties are carried out by comparing the tribological behaviors of Ti₃SiC₂ coatings deposited at different plasma powers?33kW,34kW?.It turned out that deposited Ti₃SiC₂ coating system with the plasma power of 33kW exhibits a remarkable decrease in friction coefficient and improved wear resistance due to the crack-healing and lubricant capacity of TiO₂,SiO₂ and other oxidation products.?3?Based on these studies,pre-oxidation thermal treatment subjected to various oxidation temperatures?200?,300?,400??and durations?1h,3h,5h?are performed for a better wear-resistant Ti₃SiC₂ coatings.Oxide layers that mainly consist of TiO₂ are identified on the surface of Ti₃SiC₂ coatings after thermal oxidation treatment and preferable tribological performances are obtained under the oxidation temperature of 300?and the duration of 1 h.