Effect of Wearlessness in the Surface Alloying of Steel with Bismuth

An analysis of the wearless effect for carbon steels subjected to surface alloying with metallic bismuth using the technology of short-pulse laser melting is performed. The tribological studies have been conducted in conjunction with industrial metal alloys such as gray cast iron, nickel-aluminum bronze, and aluminum alloy. Under boundary lubrication conditions, the bismuth-alloyed steel surface tested in contact with the analyzed alloys has shown ultralow value of the friction coefficient in the range from 0.04 to 0.08. It is established that a high level of fatigue strength of the aluminum alloy and the absence of adhesion with respect to a bismuth-alloyed steel surface provide conditions leading to the manifestation of the wearless effect (zero wear) at friction velocities amounting up to 9 m/s and at normal loads amounting up to 250 N. The metallographic analysis and 3D profilometry of friction surfaces have revealed that the process of self-organization of the contact zone is athermal in nature (without frictional heating) and is determined by a plastic flow of the contacting surfaces with no mutual destruction thereof.