Investigation of impact-sliding wear behavior and development of wear maps under dry sliding conditions of surface treated Ti-6Al-4V alloy

This study was conducted to obtain low-cost, mass-production-compatible, environmentally friendly surfaces with high hardness and wear resistance by applying surface treatments such as thermal oxidation at three different temperatures (600, 700, and 800 °C), pack cementation aluminizing, and hot-dip aluminizing at 750 °C on the surface of the Ti-6Al-4V alloy. Structural characterizations of the samples subjected to three different surface treatments were performed, and reciprocating wear tests were conducted under dry sliding conditions at different loads and speeds. Impact sliding wear tests were applied to the Ti-6Al-4V alloy that underwent thermal oxidation at 600 and 700 °C. As a result of the pack cementation aluminizing process, an aluminum-rich titanium aluminide layer was formed, thickening with increased process temperature. The highest hardness value of 616 HV0.025 was measured in the sample aluminized at 800 °C, where the layer consisted of the TiAl2 phase. After the thermal oxidation process, the Ti-6Al-4V alloy exhibited a structure consisting of an oxide layer and an oxygen diffusion region. The thickest oxide layer observed after 30 hours of thermal oxidation at 700 °C, is 6 μm thick. The highest hardness, 700 HV0.025, was also measured in the same sample. XRD analysis confirmed that the oxide layer consisted of the rutile phase. Wear tests conducted at 25, 350 and 550 °C showed that the sample subjected to 30 hours of thermal oxidation at 700 °C exhibited the lowest wear rate at both test temperatures, with total wear rate (impact+sliding) reductions of 54%, %34 and 37%, respectively. It was determined that reciprocating dry sliding wear resistance was improved by aluminizing and thermal oxidation at all three temperatures. After hot-dip aluminizing and subsequent diffusion annealing, a composite layer with a hardness of 461 HV0.025 was obtained. Upon reviewing the reciprocating dry sliding wear results, it was observed that as the sliding speed increased, the wear resistance also decreased for coating with hot-dip aluminizing and subsequent diffusion annealing treatment.