Research on laser quenching process of 20CrMnMo gears by finite element method and experiment

Abstract

To explore laser quenching process of 20CrMnMo gear, finite element analysis of the quenching process and laser quenching experiment were performed. First, a finite element model of laser quenching process was built, with surface effect unit was added to the 3D model of gear. Then, the load was applied by two kinds of ways including manual mode and APDL language. At last, the continuous movement of laser speckle and the distribution of temperature field along both the axial direction of tooth surface and the depth direction were simulated, and the temperature curves changed by time about nodes along the central surface and depth direction were acquired, which has important guiding significance to the parameter settings of laser quenching process. On the other hand, 20CrMnMo gears were processed by laser quenching after carburization, the tooth surfaces with different hardness values were got, which are studied using the experiments with combination of three parameters including laser power, scanning speed, and light spot diameter. Typical teeth surface were make samples and studied by SEM, and the hardening layer was measured by metallographic microscope. A good agreement in the simulation and experiment results was found. Research result shows that the optimum parameters of laser quenching about 20CrMnMo gears are the following: laser power P = 2300 W, the scanning speed v = 750 mm/min, spot diameter d = 14 mm; the maximum hardness of tooth surface is 61.4 HRC, the microstructures are compact needle and plate strip martensite, the grain size is about 9°; equivalent hardened layer depth is 1.8 mm or so.