Characterization and tribological performance of oxide layers on a gamma based titanium aluminide

In this investigation, Ti-45Al-2Nb-2Mn-1B (at%) titanium aluminide was thermally oxidised at different temperatures of 700-950 °C and at different times. Most oxidation exposures resulted in the formation of a compound layer consisting of several oxide layers, a TiO2 layer as the outermost layer on top of a layer of Al2O3 particles, a mixed layer of TiO2 + Al2O3 underneath, and TiN and Ti2AlN were found at the interface of the compound oxide layer and the matrix. The compound layers were wear tested using a ball-on-disc configuration against 10 mm diameter hard steel (AISI 52100) balls under dry sliding conditions at applied loads of 20, 50, 80 and 100 N. The oxide layers and worn surfaces were characterized using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), glow discharge spectroscopy (GDS) and microhardness measurements. Steel was transferred to the oxidised surfaces without any considerable deformation of the surfaces. In general, the wear resistance of oxidised surfaces of titanium aluminide was several times higher than that of untreated surfaces.