The 40Cr surface hardening mechanism by pre-stressed dry grinding

40Cr steel is one of the most widely used steels in machinery manufacturing. After tempering treatment, it has good mechanical properties and low-temperature impact toughness. In order to effectively improve the machining quality and surface integrity of the parts, a new machining technology, pre-stressed dry grinding, is proposed. The technology combines pre-stress grinding and hardened grinding technology in one, reasonable control of the surface stress state of the processed parts. It can change the sub-temperature quenching organization of the surface layer. Meanwhile, it has the characteristics of reducing energy consumption and conforming to green processing. In this paper, ANSYS software is used to analyze the specimen's temperature field simulation. Based on MATLAB, a non-Gaussian random function simulation is used to obtain the grinding wheel's surface with the final simulation of the surface trajectory model. The results show that with the increase of pre-stress, the surface quality of the specimen improved, and the defects, such as cracks and burns on the material's surface, are gradually reduced. Compared with the 45# steel, the Cr element hinders the growth of austenite grains and the transformation of austenite to large-grained pearlite. The metallographic organization of the hardened layer is refined and dense, and the surface roughness decreased by 38%. The study's results deepen the understanding of material removal and damage under the action of pre-stressed dry grinding technology, but the proposed method can also help realize high-performance manufacturing of 40Cr steel substrate surfaces.