Residual stresses on flat specimens of different kinds of grey and nodularirons after laser surface remelting

Laser surface remelting is one of the best procedures for surface modificat ion of ferrite- pearlite nodular irons. Using this procedure on cast irons it is possible to achieve a very high wear resistance, which can be compare d with the wear resistance of surface hardened heat treatable steels. The p roperties of the modified layer depend on the microstructure before heat tr eatment and on the amount of energy input transferred into the surface laye r of the specimen. The research work has focused on the study of residual s tresses after laser surface remelting of different kinds of grey and nodula r irons. The identification of residual stresses was performed using the re laxation method, which involved measuring specimen strain. The results of t he measured residual stresses confirm that the stresses strongly depend on laser surface remelting conditions. The measurement of residual stresses is very important in exacting dynamically loaded machine parts, which have be en subjected to different kinds of heat treatment. In designing parts desig ners very frequently demand the presence of compressive residual stresses a fter heat treatment and finish grinding of the surface, since this increase s the fatigue strength of the material and reduces the danger of fracture.