Cold compressive and tribological properties of forged and heat-treated Ti-6Al-3Mo-2Sn-2Zr-2Nb-1.5Cr-0.1Si alloy

The impact of forging and heat treatment processes on cold compressive and tribological properties (wear rate & friction coefficient) of Ti-6Al-3Mo-2Sn-2Zr-2Nb-1.5Cr-0.1Si (TC21) alloy was studied. Additionally, an investigation of worn surface texture using the Abbott Firestone curve was conducted on MATLAB and Gwyddion software. For 20 min, the samples were heated to 925 °C. They were then cooled at different rates using water quenching (WQ), air cooling (AC), and furnace cooling (FC). Following that, the samples were aged for four hours at 600 °C. The microstructure consists of retained β-phase (βr), secondary α-phase (α_s), and primary α-phase (α_p). The α_s-phase precipitated within the β_r-phase in the case of aged samples and solutions treated with AC. The results show that the highest ultimate compressive strength of 1997 MPa was obtained for the FC + Aging and the sample owing to the existence of a high-volume fraction of α_p-phase in the structure. On the other hand, the lowest ultimate compressive strength of 1473 MPa was achieved for the AC sample due to having a high amount of fine α_s-phase. Comparing the WQ and WQ + Aging conditions, it is clear that the WQ + Aging condition shows 51% enhancement in wear property due to the presence of the α_s-phase after applying the aging process. On the other hand, the wear properties of AC and FC after the aging process improve by only 18% and 4%, respectively. There is a slight variation in the friction coefficient values after the solution treatment process at different cooling rates (WQ, AC & FC). However, after applying the aging process, there is a clear change in WQ + Aging and AC + Aging conditions, where the value of the friction coefficient decreases by 19% and 12%, respectively. For the Abbott Firestone technique, the forged sample has a lower percentage of exploitation zone (77%) and a larger percentage of high peaks (22%). On the contrary, FC and FC + Aging samples have a higher percentage of exploitation zone (81%) and a lower percentage of high peaks (17%) compared to other samples.