Laser quenching process parameters

Laser surface quenching is an intricate process involving rapid heating and rapid cooling. The dimensional parameters of the laser-hardened layer (hardened layer width, hardened layer depth, surface roughness) and performance parameters (surface hardness, wear resistance, microstructural changes) depend on the laser power density (laser power, spot size), scanning speed, material properties (composition, initial state), and surface pretreatment of the material, among other factors. They are also related to the geometry and dimensions of the treated part and the thermodynamic properties of the laser-affected zone. Under constant other process conditions, the main process parameters—laser output power P, scanning speed V, and spot size D acting on the material surface—collectively determine the holding temperature and holding time of the laser quenching process. The influence of these three parameters on the laser surface quenching effect is as follows: the depth of the hardened layer is directly proportional to the laser power and inversely proportional to the spot size and scanning speed.

Additionally, the selection range of each parameter value should be considered. D should not be too large, and V should not be too small, to avoid excessively low cooling rates that prevent martensitic transformation. Conversely, when the laser output power is too high, surface melting may occur, affecting the surface geometry. The smaller the ratio of the critical transformation temperature of austenite to the melting point of the material, the wider the allowable temperature range for phase transformation, and the deeper the hardened layer depth. Furthermore, factors such as the scanning pattern (graphics) of the hardened band, the proportion of hardened area, the width of the hardened band, the gas blowing conditions in the laser-affected zone, the optical system, and the beam focal length also have certain effects on the quality of laser surface quenching.