Laser hardening process simulation for mechanical parts

Abstract

ABSTRACT In this paper a numerical simulation of laser hardening process is presented. The Finite Dierence Method(FDM) was used to solve the heat transfer and the carbon diu sion equations for a de“ned workpiece geometry.The model is able to predict the thermal cycle into the target material, the phase transformations and theresultingmicro-structuresaccordingtothe laserparameters,the workpiecedimensions andthe physicalpropertiesof the workpiece. The eects of the overlapping tracks of the laser beam on the resulting micro-structures is alsoconsidered.The initial workpiece micro-structure is taken into acco unt in the simulation by a digitized photomicrographof the ferrite perlite distribution before the thermal cycle.Experimental tests were realized on a C43 plate and the good agreement between the theoretical and exper-imental results is shown.Keywords: Laser hardening, numerical simulation, process planning. 1. INTRODUCTION LaserHardeningofsteel componentsis a stable processwhere veryhard, wearresistancesurfacescan be uniformlyobtained into the workpiece when the correct process pa rameters are set. It allows to treat complex shapes,usually very diculty to realize with conventional surface hardening, with less distortions than that caused by”ame or induction hardening.This process is becoming widely used in industrial environment due to the development of new generationlaser sources. Diode laser with high power density, high eciency and very uniform distribution are commonlyavailable together with the last generation of high power “ber lasers. These new types of sources usually havevery compact resonators like the diode ones, or the laser beam can be easily delivered to the workpieces bymeans of optic “bers, like the “ber or the Nd:Yag lasers. For these reasons, surface heat treatment, usually anoutsourcing operation for the small-medium mechanical company, always more often is realized from the samecompany which realize the cutting operations. Many eorts are nowadays conducted to integrate in a machinecenter for metal cutting the operations of surface hardening considering the laser beam as a conventional tool.The economic aspect is crucial for the development of the laser technology in Industry. For the completeexploitation of the laser resources, in fact, it is fundamental to consider the technological advantages of thelaser together with the high capital costs of the systems: widespread use of lasers in industry for heat treatingmainly depends on the cost of the treated component. In general, laser hardening can be more economicallyapplied respect to the conventional processes when batches of small dimensions or when complex shapes mustbe hardened. In this direction, the challenge is to increase the ”exibility of the laser technology.Laser hardening is a quite complex process which involves many parameters:€ the laser parameters like the power density and distribution, the spot dimension and the laser beam velocitywhich determine the heat cycle in the workpiece;