Têmpera superficial a laser no aço AISI 300M

Abstract

Surface engineering aims to improve the performance of materials through surface transformations. Surface modifications may be carried out by the coating application means or by thermal or thermochemical treatments. In this work, the surface change is obtained by the laser surface tempering of Nd: YAG, which is based on the application of a laser beam with high power on the surface of the material, to reach in seconds the selected austenitization temperature in a thin layer. With the removal of the laser beam, the marked thermal gradient originated between the layer and the core produces self-annealing, transforming the microstructure of the austenite surface to martensite. Among the advantages of using Nd: YAG in surface quenching we can mention: higher thermal conductivity, shorter wavelength and the possibility to perform quenching in localized regions. This work analyzed the effect of the power and processing speed of the Nd: YAG laser surface tempering on the microstructure of the 300M steel. The results presented are concerning surface hardness and the depth of hardening and the corresponding microstructure types, thus allowing to identify the conditions that provide the best results for 300M steel. The best laser quench parameter for Nd: YAG was at a speed of 20 mm/s, a power of 400 W providing a layer in the order of 20 μm and a hardness of 503 HV.