Tribological Response of Mechanical Attrition Treated Surface of AISI 316L Steel: The Role of Velocity of Colliding Balls

Current work focuses on studying the tribological response of the severely deformed surface of AISI 316L steel specimens using a ball-on-disk tribometer. Specimens are investigated under dry and lubricated (using engine-oil) conditions using different loads and sliding velocities. Surface mechanical attrition treatment (SMAT) using 6 mm diameter balls improves the surface hardness of steel by 56%. The wear performance of the severely deformed surface is significantly better than the non-treated steel under the investigated wear conditions. Under the lubricated condition, an improvement in the tribological response of attrition treated specimens is substantially greater than in the dry sliding condition. Steel surface collided with higher velocity balls shows the maximum reduction in wear-rate, which is about 44% and 88% under dry and lubricated conditions, respectively. Under the lubricated condition, the steel surface treated with a lower velocity of the colliding balls shows about a 97% reduction in wear-rate. The lowest specific wear-rates of the attrition treated specimens are 2.32 × 10⁻⁴ and 0.11 × 10⁻⁶ mm³/(N m) under dry and lubricated conditions, respectively. The contact angle of the lubricating engine-oil on the attrition treated surface (32.65–41.75 deg) is higher than the non-treated surface (19.2 deg). The coefficient of friction (COF) decreases with an increase in the contact angle on the treated surface. COF of the attrition treated specimen ranges from 0.04 to 0.07 under the lubricated sliding condition.