Research Of Laser Surface Hardening Of Carbon Structural Steel And Cr12MoV

High-energy lasers are increasing being used in the industry for laser surface heat treatment to modify metal surface structures through intense heating followed by self-cooling. In laser quenching, a thin layer of the substrate is rapidly heated well into the austenitizing temperature range by laser heating and is cooled subsequently at a very fast rate, due to self-quenching by the conduction of heat into the bulk body, to produce a martensitic structure.Rapid heating and cooling are the key characteristics of laser quenching that enable the formation of a novel microstructure and thereby improve the hardness and the wear resistance. To achieve high wear resistance, the combination of the hardness, case depth, profile and microstructure of the quenched zone is important. Because there is so many factors influencing the laser surface hardening process that make it very hard to control the quality during the performance. This industrial application is limited by the poor repeatability and transportability of laser machining process.In order to enhance the potential for such laser machining process, it is essential to get better understanding of the physical process associated with the laser material interaction and the effect of various operating parameters on the performance, and then optimization the mostly important parameters and find the effective method to exactly control related parameters.This paper operate laser surface hardening experiment using 3kW CO2 continuous wave laser, the experiment materials are premium carbon steels (20#,45#) and Cr12MoV steel, The effect of process parameters (such as laser power, travel speed , overlapping ratio etc) on quenching quality (profile, microstructure, case depth and hardness etc) was examined. Base on experiment result, analysis the most influencing parameter on surface hardening quality, choose the suitable process parameter and then optimize the laser quenching process. These valuable process parameters meeting the experimental conditions and the method of controlling quality can be used in productive practice, it will promote the industrial application of laser surface hardening process on steel surface hardening specially die steel.We obtain the optimum parameters of laser surface hardening process by laser surface quenching experiments of single track quenching and multiple tracks quenching based on laser processing system of ChongQing Institute of Optics and Mechanics: for 45 steel laser power is 1350w, traverse speed is 1200 mm/min and overlapping ratio is 20%; for 20 steel, laser power is near to 1350w, it need lower overlapping ratio comparing to 45 steel; for Cr12MoVsteel, laser power is 1500 w and overlapping ratio is lower than 15%.