In automotive, energy, mechanical and plant engineering industries the processing of high-strength alloys and composite materials has increased rapidly over the last decades. This requires production tools with e.g. high strength, hardness and wear resistance. To enhance tool, repair welding processes are more efficient and resource-saving than the purchase of new tools [1,2]. Laser deposition welding is the preferred welding process for high-alloyed, complex tools applied for injection molding or precise cutting with high sensitivity to thermal distortion due to its high-density, but lower heat input per unit length compared to arc welding [1]. In this process, the heat-affected zone and, thus, residual stress and cracking in the weld metal are reduced. Compared to arc welding processes, laser welding is further advantageous due to more precise positioning and focusing of the beam, more process flexibility as well as application in narrow areas [1].
Manual laser deposition welding is used to build up or repair filigree structures or larger areas. Commonly solid wires with diameters of about 0.1 mm are applied. However, the processing of such thin wires is quite challenging, even more, when high-carbon, high-alloyed steels are applied. Those high-performance steels are, however, very attractive for tool repair to maintain or overcome the hardness and wear resistance of the substrate material. For wire processing, several intermediate heat treatments, and a high forming force would be necessary. An alternative approach to this complicated and costly processing route is the powder-in-tube method, which was applied in the present study to develop a novel filler wire. The nominal composition was given by the desired tool steel in total, but the constituents were separated into a well-formable shell material with poorly formable constituents placed inside. Such wires are well-known for arc welding, but have not been applied yet for laser deposition welding.
The powder-in-tube-composite were cold worked with a 4-plunger rotary swager from 20 mm to an outer diameter of about 1 mm. For validation, those wires were processed by manual laser deposition welding to receive multilayer welding layers with high quality and hardness values of at least 700 HV0.1.