Comparison of laser quenching technology for gears

As the core part of most machines, the performance of gears directly determines the degree of mechanical excellence. In the process of machining, the biggest problem is heat treatment deformation. In the process of quenching, the distortion of the workpiece is too large, and it is still difficult to eliminate the deformation in the fine grinding, which results in the effective utilization rate of the material in the gear production is only 30% ~ 50%, which not only increases the production cost, but also causes a huge waste of resources. Laser quenching is a new technology developed for the defect of gear. The energy density of laser beam is as high as 103 ~ 105W / cm2. After scanning, the surface hardening layer of the part immediately absorbs the light energy and converts it into heat energy. The temperature rises sharply and exceeds the phase transformation point of the material to form austenite. Because the heat transferred has not reached the matrix, High temperature gradient is formed in the low temperature matrix and the high temperature heat treatment part. Because the scanning time of laser quenching is very short, the heat treatment zone is quenched due to the instantaneous cooling, the austenite on the surface changes into martensite, and the content is very high, so the purpose of surface quenching of parts is achieved. Laser quenching of gears has been widely concerned and studied at home and abroad.

The conventional gear quenching process includes carburizing quenching, induction quenching, flame quenching, salt bath quenching, etc. In the process of conventional heat treatment, there will inevitably be many kinds of tissue stress and thermal stress, which will directly affect the surface roughness and machining accuracy of the gear. Because of the unstable heat treatment quality, it is easy to cause the deformation of the gear positioning base surface and tooth surface to be too large, warping deformation and other problems, leading to a large number of gear scrapping.

Laser quenching has obvious advantages in heat treatment of gears, such as high hardness, good wear resistance, small deformation, precise and controllable hardening layer depth and area, short production cycle, clean and environmental protection, etc. In addition, some researchers have compared the hardness of gears treated by various processing methods, which shows the advantages of laser quenching.

1) At present, the laser quenching and scanning methods of gear have not met the requirements of even heating on the surface of gear teeth.

2) Due to the variety of gear materials, the best laser quenching parameters of gears with different materials are quite different, which leads to the lack of guidance in many existing research conclusions. Therefore, it is necessary to study and sort out the best laser quenching parameters for gears of various common materials, and to get a unified standard for reference.

3) The process of gear laser quenching is complex, so it is necessary to improve the process method to realize automatic and numerical control.