Reciprocating surface grinding of a gamma titanium aluminide intermetallic alloy

Abstract

The paper initially reviews the published grinding research on titanium intermetallics. Details are then presented of a 4 factor, 2 level, full factorial experiment, undertaken to assess the grindability of a gamma (γ) titanium aluminide Ti–45 Al–2 Nb–2 Mn+0.8 vol.% TiB 2 XD™ when surface grinding with SiC wheels. Tests involved variations of abrasive grit size, wheel grade, wheel structure and depth of cut. Cutting force, workpiece surface roughness ( R a, μm) and subsurface microhardness data are detailed. Depth of the cut was the most significant factor affecting the magnitude of force, with normal and tangential forces varying in the range 20–50 and 5–15 N per unit width of cut, respectively. Surface roughness of the workpiece was also largely dependent on the depth of the cut and ranged from 0.5 to 4.5 μm R a. Grit size was identified as the most significant factor when assessing maximum subsurface hardness. In the worst case, values increased to 550 HK at a depth of 10 μm, before returning to the bulk hardness of 350 HK between 200 and 500 μm below the ground surface. No serious microstructural damage, in the form of cracks, HAZ or recrystallisation was observed. The results suggest that the particular gamma alloy tested was significantly easier to grind than standard titanium alloys such as IMI318 (Ti–6Al–4V). This is in sharp contrast to single point turning, where the reverse is true.