Abstract
Abstract The influence of plasma hardening on the processes of hardening of heavily loaded high-wear parts of the working bodies of tillage machines has been studied. It is shown that during surface plasma hardening of a plough share made of structural steel 65G in a hardened zone with a thickness of ~0.8 mm, a gradient-layered (mixed) structure is formed, consisting of a finely dispersed mixture of austenite decomposition products with microhardness decreasing from the surface to the central zones in the range 429.3–215.2 HV0.5. It is confirmed that the creation of a gradient-layered structure and the features of its formation after surface plasma treatment are associated with ultrahigh heating and cooling rates, which are unattainable with traditional heat treatment methods. It has been established that when the surface of a part is heated by a plasma arc, the main characteristics of the thermal cycle: the maximum heating temperature, the residence time of a given point of the part above the upper critical point Ac3, the heating and cooling rates are determined by a combination of the parameters of the plasma hardening mode and are interrelated, which indicates the need to strictly follow the selected mode to obtain a given depth and hardness of the surface layer.