The use of factorial design and response surface methodology for fast determination of optimal heat treatment conditions of different Ni–Co–Mo surfaced layers

Surfacing is a very promising process when applied to repair and manufacture of new machine and tool parts. The development of surfacing has been strongly supported by the development of filler materials such as cored wires and alloyed agglomerated powders. Procedures of manufacturing cored wires and alloyed agglomerated powders are comparatively simple, which permits a fast preparation of filler materials showing different compositions and designed for surfacing of mechanically, chemically and/or temperature-resistant layers. The paper deals with the procedure of selecting suitable conditions of post-heat treatment of surfaced layers applied to the manufacture of high-quality layers made from different Ni–Co–Mo alloys on adapted flat specimens made from St 44-3 structural steel. Different alloys related to commercial maraging steels were surfaced by submerged arc welding using home-made filler materials. Taking into account that the properties of a surfaced layer usually differ from those of commercial alloys in the as-delivered state it is necessary to find optimum heat-treatment conditions for the surfaced layer. In our research, factorial designs and a response surface methodology were applied to the determination of the optimum heat-treatment conditions of the surfaced layers made from different alloys.