Dry-Sliding Wear Mechanisms of Shot-Peened Additive Manufactured Alpha Titanium Featuring TiB Particles

The load-induced dry-sliding wear behavior of alpha titanium (Ti) with low amount of boron (< 1 wt%) samples made through plasma transferred arc solid free form fabrication process were studied in the untreated and hardened shot-peened surface conditions. Shot peening conducted at 90 psi for two minutes for 100% coverage with S-550 steel shots, was found to lead to an increase in surface hardness, with a depth of penetration of approximately 1 mm. While shot peening in this scheme was found to have a limited influence on COF and wear rates, it did influence the wear mechanisms observed. Untreated samples had a shift in wear behavior from low to high loading conditions. Dominating wear mechanisms at low loads (<= 10 N) for untreated samples were oxidative and abrasive wear accompanied by weight gain of the steel counterface balls. At higher loads (> 10 N), untreated samples experienced weight loss of the steel counterface balls and severe plastic deformation with the formation and onset delamination of mechanically mixed layers (MML). Comparatively, shot-peened samples exhibited limited changes in wear behavior, remaining dominated by oxidation wear over the loading range. With oxidation wear dominating and the shot peening treatment inhibiting the formation of a MML and its delamination, it is hypothesized that the transition to severe wear may be delayed to higher loads from this treatment.