Hardness prediction considering the influence of alloying elements in laser hardening based on a 3D thermal model.

Taking the influence of alloying elements into consideration, a hardness prediction model based on a newly proposed parameter named actual carbon diffusion time (ACDT), which was calculated by combining temperature history with carbon diffusivity, is developed in this paper. The hardness distribution was directly derived from a 3D thermal model, which was constructed to simulate the laser surface hardening of AISI 1045, and from which the temperature history was also obtained. Using this 3D thermal model, the geometric characteristics after laser hardening (e.g., the width of the hardened layer, the depth of the phase change layer) were determined according to the martensitic transformation. The influences of the scanning speed and the laser power on the geometric characteristics were investigated, and the relations among the geometric characteristics after laser hardening were further determined. The laser hardening experiments with various parameters were conducted, and it was found that the hardness can be accurately predicted using the developed hardness prediction model (R-squared, 97.0%). The proposed parameter ACDT, as the core of the hardness prediction model in this paper, broadens the way for hardness prediction in laser hardening with the alloying effect involved.