Design of friction and wear resistant titanium- and cobalt-modified nickel-base repair alloys by spray forming

Abstract

Powder injection molding (PIM) is a newly developed method for repairing gas turbine components in recent years. However, the PIM method needs a sacrificial binder, which increases working procedure and cost. To overcome this disadvantage, a new method of maintenance, i.e. spray forming (SF) technique, is put forward in this study. Three kinds of Ni-base repair alloys have been designed and prepared by the SF process. And these alloys were subjected to friction, wear and material analysis tests. Results reveal that the alloy with high titanium and cobalt content has the best friction and wear resistance. The increase in titanium and cobalt content will result in the increase of γ/γ′ misfit, grain size, and coherent γ′ size, and enhance the formation of good oxides lubricants, which leads to a decrease of the coefficient of friction. Moreover, with increasing titanium and cobalt content, the predominant wear mechanism changes from delamination wear to abrasive wear and adhesive wear. The high titanium and cobalt content give a large improvement in wear resistance by strongly hindering dislocations motion and reducing crack growth rate, which resists delamination wear.