Research Of Semiconductor Direct Output Laser Transformation Hardening Based On Temperature Control

With the improvement of the semiconductor laser power and beam quality, the semiconductor lasers have been widely used in the application of surface modification. At the same time, direct output semiconductor laser has a lot of applications in automobile, mould, hardware, light industry, machinery manufacturing, and many other industries, because of its’ shorter output wavelength as well as its’ higher photoelectric conversion efficiency and material absorption rate.Laser transformation hardening technology, as an important part in material surface modification, solves many problems that conventional heat treatment process can not solve, its technical advantage is more and more obvious. However, there are many factors affecting the quality of laser phase transformation hardening process, so it is difficult to control the quality of martensite phase transformation layer in the practical application, which restricted the application of laser transformation hardening technology.In order to simplify the process of laser phase transformation hardening and improve the quality of the martensite phase transformation hardening layer, a semiconductor direct output laser processing system was built which can realize temperature control in laser process. On the basis of the hardware platform, LaserM master control software was developed based on Labwindows/CVI development environment, and fuzzy control algorithm was designed for temperature control in the process of laser processing.And then, the contrast experiment of laser phase transformation hardening was designed in the mode of constant laser power and temperature control. The experiment proved that the consistency of depth and hardness of the transformation hardening layer was better in the temperature control mode contrast to that in the constant laser power mode. Then a series of orthogonal experiments were designed in the mode of temperature control, which proved that the depth of transformation hardening layer was proportional to the set temperature and the width of the laser spot, and under the same laser transformation hardening control temperature, the hardening depth increased firstly and then decreased with the increase of the scanning speed. In order to get deeper depth of hardening, and further research the influence of scanning speed on the depth of hardening layer, laser transformation hardening optimization experiments were designed in temperature control mode. The depth of phase transformation hardening was up to 1.25 mm, and microstructure analysis of the samples showed that the composition of laser transformation hardening zone and the differences of organization impacted by cooling rate were the main reason caused the property difference in hardened layer.In order to further research the influence of the scanning speed and control temperatureon the depth of martensite phase transformation hardening layer, a three-dimensional lasertransformation hardening simulation model was built with the COMSOL Multiphysics,using the determinant conditions based on non-equilibrium austenite transformationtemperature and the martensitic critical conversion rate. Comparing with the experimentalresults, the model can predict the laser transformation hardening layer depth in laserhardening process accurately.