Sliding wear behaviour of two gamma-based titanium aluminides

Lamellar Ti–48Al–2Nb–2Mn (at.%) and Ti–45Al–2Nb–2Mn–1B (at.%) titanium aluminides have been wear tested using a ball-on-disc configuration against a 10-mm-diameter hard steel ball under dry sliding conditions at applied loads of 3.5, 5, 10 and 20 N. The worn surfaces have been characterised using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and microhardness measurements. Plastic deformation and ploughing have been observed on the worn surfaces. The stresses imposed by friction near the surface caused a slight deformation of lamellae followed by interlamellar boundaries slip resulting in the inter-lamellar cleavage and subsequently their fracture. Micro-fracture from the inter-lamellar cracks resulted in the separation of fine-grained and flake-like debris.