Residual stress state after the laser surface remelting process

Residual stresses are a result of elasto-plastic deformations induced in th e workpiece material during the heat treatment process. The extent and magn itnde of internal stresses depend on temperature conditions in heating and cooling and physical properties of the workpiece material. This contributio n discusses the extent and distribution of residual stresses after laser re melting a thin surface layer on ductile iron 80-55-06 (ASTM specification) or Gr 500-7 according to ISO, Residual stresses are not only induced by tem perature differences but also result from stresses due to microstructural c hanges between the surface and the core of the specimen subsequent to cooli ng to the ambient temperature. The distribution and extent of residual stre sses in the remelted thin surface layer depend mostly on melt composition a nd cooling conditions, Different rates of solidification and subsequent coo ling of the remelted layer are reflected in the volume proportions of the c reated cementite, residual austenite, and martensite in the microstructure, The rate of heating and cooling of the thin surface layer is a function of laser power, beam diameter on the workpiece surface, and interaction time. In addition, the number of passes of the laser beam over the workpiece sur face and different degrees of laser trace overlapping were increased to see how these can affect the thermal conditions in the workpiece. To determine the residual stresses, the relaxation method was used, This is based on me asuring the specimen strain during electrochemical material removal.