High temperature friction and wear behavior of cold-sprayed Ti6Al4V and Ti6Al4V-TiC composite coatings

Abstract

The poor wear resistance of titanium and its alloys often results in galling and high wear rates. One method to improve their wear resistance is by hard secondary phase reinforcement to create a metal matrix composite, which can be utilized in the bulk or as a coating. In the present study, Ti6Al4V coatings and Ti6Al4V-TiC metal matrix composite coatings were deposited on mild steel substrates using cold spray process and their dry sliding wear behaviour was studied over a static temperature range of 25-575 º C. Tests were performed using a unidirectional ball-on-disc tribometer with WC-Co sphere as the counterface at a load of 2.5 N and sliding velocity of 2.1 cm.s -1 . Wear rate and coefficient of friction (CoF) decreased with an increase in temperature and composite coatings exhibited higher wear resistance at all temperatures. Below 200 º C, abrasive wear characterized by ploughing by wear debris resulted in high wear of Ti6Al4V coatings, whereas formation of tribolayers led to lower wear of composite coatings. At elevated temperatures (> 200 º C), oxide glaze layers formed on both coatings were composed of WO3, TiO2 and CoWO4. Electron channel contrast imaging of the wear track cross-sections showed no splat debonding, less extent of recrystallization and larger grain sizes (at 575 º C) in composite coatings compared to Ti6Al4V.

Temperature-mediated tribological characteristics of 40CrNiMoA steel and Inconel 718 alloy during sliding against Si3N4 counterparts

“…In contrast, the COF of Inconel 718 alloy decreases slowly before 400 ℃, and a quick decrease occurs after 400 ℃. These results imply temperature-mediated frictional features for two as-received alloyed materials, which are predominantly tailored by the developed tribolayer over the tribologically contacting surface [29].…”

Microstructure and friction-wear performances of laser-cladded nano-CeO2–reinforced NiCoCrAlY coatings at high temperature

“…Figure 9(a) shows the wear mechanism of NiCoCrAlY coating. The oxide layer was formed on the worn track at a high temperature because of the oxidation of alloy elements, 36,37 and the tribo pair rubbed violently with the coating and produced a large amount of debris on the marked green zone. At the same time, at high temperatures, the welding junctions occurred on purple zone between the tribo pair and the coating, which lead to adhesive wear.…”

The role of metal powder properties on the tribology of cold sprayed Ti6Al4V-TiC metal matrix composites

“…Initial source flow of the ceramic, Qsc, is often very small unless the composite is poorly engineered with very low cohesive strength. A second common reason for good tribological performance for MMCs is that ceramic particles tend to enhance the formation of tribolayers on the surface [6,27,35], an important mechanism to reduce wear at longer sliding distances (see Fig 15b). The tribolayers may be in the form of tribo-oxides, sometimes called glaze layers, or simply mechanically mixed layers (MMLs).…”

“…Using CS, we have studied previously the incorporation of TiC particles into Ti alloys, including cp-Ti [2] and more recently Ti6Al4V-TiC [27]. In the original work on Ti-TiC, the composites were tested for sliding wear using a spherical WC-Co counterface at a normal load of 0.5 N (~ 0.5 GPa initial maximum Hertzian contact stress).…”

“…The martensitic lath microstructure of the plasma gas atomized powders results in poor particle deformability and porosity in the final deposits, hence a more deformable powder with equiaxed microstructure was found as an alternative. In our previous study [27] of cold sprayed Ti6Al4V-TiC MMCs, their tribological behavior was tested at different temperatures and at a higher load of 2.5 N (~ 0.8 GPa initial maximum Hertzian contact stress) using a spherical WC-Co as counterface. Based on the study, it was found that the reinforcement of carbide particles improved the wear resistance at lower temperatures whereas tribo-oxidation led to low wear of both metal and composite coatings at elevated temperatures.…”