Friction Stir Surfacing of Cold Sprayed Bainitic Steel

Abstract

A superficial composite layer was produced by friction stir surfacing (FSS) on high strength bainitic steel, cold sprayed with the Cu-Y2O3-ZrO2 and Zn-Y2O3-ZrO2 metal-oxide powders. The FSS resulted consolidation of the elemental powders in the cold sprayed (CS) layer with some melting of Zn and Cu. The formation of a continuous, adherent layer on the steel surface facilitates closing of large pores at the coating-substrate interface. The consolidated layer on the steel surface showed comminution of the coarse oxide particles and concomitant reduction in the average particle size. The FSS resulted in a composite layer consisting of the hard martensite structure up to 0.4 mm from the surface. The region just below the top solidified layer exhibited the soft ferrite and pearlite structure with narrow microstructural bands of fine martensite. The net torque and in-plane forces for the composite layer production are significantly different from the Zn and Cu cold sprayed layers.