Technical Feasibility of Laser Dissimilar Welding of Superalloys on Casted Nozzle Guide Vanes

An increasing degree of automation is required both in the automotive and aircraft industry in order to allow scrap reduction and flexibility. In this frame, the shift from arc welding to laser beam welding is being investigated for a number of applications on metals in aerospace engineering, where strict standards apply. In comparison with conventional welding methods, a number of advantages are benefited; nevertheless, when moving to a new technology, some issues must be addressed. Hence this study is aimed to investigate laser dissimilar welding of real metal components, in order to assess the technical feasibility as well as to discuss set-up and operating issues in view of the implementation of the process for actual industrial application. A second-stage stator of low-pressure turbine is considered: lightening of the airfoils of the nozzle guide vane is achieved thanks to inner hollows which are drained from wax upon casting; afterward, the core exits on the outer side of the nozzle must be conveniently closed off by means of metal plates. Joining of the plates to the nozzle is performed by fusion welding along the edge of each plate and a condition of dissimilar welding is in place, being the nozzle and the plates made of C1023 and Nimonic 75, respectively. A mixed factorial plan has been arranged, laser power, welding speed and focus position being the leading processing parameters; a convenient welding set-up is proposed. Reasons are given for the implementation of laser beam welding as an alternative to conventional arc welding.