X. H. Cui

Wear Characteristics of Ti-6Al-4V Alloy at 20–400°C

Tribo-oxides of titanium alloy are usually reported to provide low protection from wear. However, in this research, tribo-oxides provide a protective effect for wear. Dry sliding wear tests were performed for Ti-6Al-4V alloy under loads of 50–250 N at 20–400°C. Ti-6Al-4V alloy presented different wear behavior at 400°C than at 20–200°C. At 20°C, the wear loss increased linearly with increased load. The wear loss at 200°C marginally increased under 50–150 N loads and increased rapidly under a load of 200 N, slightly higher than at 20°C. At 400°C, the wear loss decreased under loads of 50–100 N, slightly increased and had the lowest value under loads of 100–200 N, and finally increased rapidly at loads above 200 N. The prevailing oxidative mild wear and the lowest wear loss at 400°C were attributed to the protective effect of tribo- oxides.

Wear and Friction Characteristics of a Selected Stainless Steel

Dry sliding wear tests were performed for 3Cr13 steel with various tempered states at 25–400°C; wear and friction characteristics as well as the wear mechanism were explored. With an increase in test temperature, the wear rate decreased accompanied by an increase in tribo-oxides. The fluctuation of friction coefficient was slight at 25–200°C but became violent at 400°C. At 25–200°C, adhesive wear prevailed due to trace or less tribo-oxides; at 400°C, oxidative wear prevailed with the predominant tribo-oxides of Fe3O4 and Fe2O3. It can be suggested that the antioxidation of the stainless steel postponed the occurrence of oxidative wear to a higher test temperature. For adhesive wear, the wear resistance, roughly following Archards rule, was directly proportional to hardness besides the specimen tempered at 500°C with grain boundary brittleness. But for elevated-temperature wear, a better wear resistance required thermal stability and an appropriate combination of hardness and toughness.

Comparative Study of Wear Behaviors of a Selected Titanium Alloy and AISI H13 Steel as a Function of Temperature and Load

A comparative study of the wear behaviors of a selected titanium alloy and AISI H13 steel as a function of temperature and load was performed on a high-temperature wear tester. The titanium alloy and H13 steel presented totally different wear behaviors with the variation in temperature and load. Their behaviors are suggested to be attributed to the protective ability of tribo-oxides and the thermal softening resistance of the matrix. Compared to H13 steel, the titanium alloy presented poor room-temperature wear resistance, excellent high-temperature wear resistance, and an extremely protective function of tribo-oxides.

Effect of Various Nanoparticles on Tribo-Layers and Wear Behavior of TC11 Alloy

Multilayer graphene (MLG), Fe2O3, and their nanocomposites with various proportions and amounts were applied as additives and directly participated in the formation of tribo-layers during sliding wear of TC11 alloy against AISI 52100 steel. Their ingredients and amounts were found to exert substantial effects on the additive-containing tribo-layers and wear behavior. Irrespective of the added amount of MLG or Fe2O3, the formed tribo-layers, because of the lack of load-bearing or lubricant capacity, readily lost stability and protection function, causing a high wear rate. However, a small quantity of MLG/Fe2O3 nanocomposites could result in a remarkable decrease in the wear rate. This was attributed to the stable existence and continuous protection of a friction-reduced and wear-resistant double-layer tribo-layer. In particular, Fe2O3-rich nanocomposite additives produced more protective tribo-layers to markedly improve the wear resistance of TC11 alloy.

Variation of wear behavior of H13 steel sliding against different-hardness counterfaces

Dry sliding tests for H13 steels sliding against different-hardness counterfaces were performed in air under a load of 50–300 N at 25–600 ℃ on a pin-on-disk elevated temperature tester. The hardness of the counterface was noticed to appreciably affect the wear behavior of H13 steel. When H13 steel slid against a hard counterface (55 HRC), the wear rate increased with an increase of temperature. As the load increased, the wear rate marginally increased at 25 ℃ and 200 ℃ but rapidly increased at 400 ℃ and 600 ℃. When H13 steel slid against a softer counterface (42 HRC), the wear rate roughly decreased with an increase of temperature besides 600 ℃. As the load increased, the wear rate rapidly increased at 25 ℃ but slightly increased at 200 ℃, 400 ℃ and 600 ℃. The large variation of the wear behavior of H13 steel was attributed to the competition of the wear-reduced function and the delamination of tribo-oxide layers. At elevated temperature, the tribo-oxide layer readily delaminated under the abrasive action of the hard counterface; conversely, it stably stayed on worn surfaces to take a wear-reduced function for the soft counterface. Adhesive wear prevailed for the hard counterface at 25–200 ℃ and the soft counterface at 25 ℃. For the soft counterface at 200–600 ℃, oxidative mild wear prevailed, but for the hard counterface, at 400–600 ℃, a mild-to-severe wear transition of oxidative wear occurred.