Experimental and Numerical Analysis of Grinding Burn and Surface Layer Modification Depth after Case Hardening and subsequent Surface Grinding

Abstract

Heat treatment and machining processes are usually analyzed in two independent simulations. Instead, in this work, a process chain simulation of case hardening and subsequent surface grinding is performed with the aim of taking into account overall tempering effects such as hardness reduction, retained austenite transformation and precipitate formation induced by both processes. Hardness and microstructure distribution resulting from the case-hardening simulation are used in the grinding simulation. The thermal load applied to the material by surface grinding is simulated by a moving heat source using the measured contact area, specific grinding power and the contact length. The thermal process limits are deliberately exceeded by increasing the depth of cut in order to generate grinding burn in form of tempering zones. A comparison of experimental and simulated carbon depth profile and hardness depth profile validate the models. The formation of tempering zones and accompanying changes in hardness can be predicted regarding their modification depth by means of simulated cementite precipitation as well as tempering time. This allows to determine the thermal process limit in grinding without extensive and cost-intensive metallographic measurements.