ANALYSIS OF DIFFERENT LASER WELDING PROCESSES FOR JOINING HARDMETALS TO STEEL

摘要

Laser welding has been investigated as a potential technology for joining hardmetals to steels for tool manufacturing industry, due to its particular characteristics such as low heat input and narrow fusion and heat-affected zones, which minimize microstructural modifications, residual stresses and distortions. Hardmetals have good high temperature and wear resistances together with high mechanical strength which make them suitable for applications like tool manufacturing industry. The poor ductility exhibited is of major concern when welding has to be used. This paper describes the work performed aiming to study the weldability of hardmetals with 6 and 12 % Co in dissimilar welds to a tool steel widely used in tool manufacturing industry with different commercially available lasers including a recent high power fibre laser. Laser welding was performed in order to analyse the effect of major processing parameters and the joints evaluated for microstructural analysis under Scanning Electron Microscopy with Energy Dispersion Spectroscopy (EDS) and mechanical resistance through three point bending tests and residual stresses measured by X-ray diffraction. Mathematical modelling of the welding process was done using a market available software regarding the thermal and residual stress fields and validated with experimental data.