Microstructure and wear behavior of TiAl3 matrix self-lubricating composites by addition of fluoride solid lubricants

Abstract

The microstructure of TiAl3 composites with addition of different weight contents of solid lubricant (LiF, NaF, CaF2, and 38% CaF2-62% BaF2) were observed by scanning electron microscopy. Hardness, bend strength, and fracture toughness tests were carried out on an electron omnipotence testing machine. The friction and wear tests were performed using a high-temperature pin-ondisc tribometer at different friction conditions such as different loads, different sliding speeds, and different working temperatures. The results show that TiAl3 composites with 38% CaF2-62% BaF2 solid lubricant exhibit higher bending strength and fracture toughness than composites with other solid lubricants. In addition, the wear rate of TiAl3 composites with 38% CaF2-62% BaF2 solid lubricant is lowest in all composites. It is attributed to 38% CaF2-62% BaF2 solid lubricant forming a compact film on the wear surface of TiAl3 composites. The compactfilm-forming mechanism is attributed to fluoride particles forced out of the reservoirs due to its high thermal expansion coefficient.