A Novel Technique to Assess the Effect of Machining and Subsurface Microstructure on the Fatigue Performance of Ti-6Al-2Sn-4Zr-6Mo

¹ Department of Materials Science and Engineering, The University of Sheffield, Sir Robert Hadfield Building, Mappin St, Sheffield, S1 3JD, UK
² Advanced Manufacturing Research Centre, Advanced Manufacturing Park, Catcliffe, Rotherham, S60 5TZ, UK
³ Rolls-Royce plc, PO Box 31, DE24 8BJ, UK

^* DSuarezFernandez1@sheffield.ac.uk

Abstract

Aerospace titanium components are manufactured under the strictest standards in order to ensure the highest quality. To develop highly efficient machining processes, extensive research and investment is necessary. For the specific case of rotating titanium critical components, large quantities of forged workpieces are machined to determine the effects of the different machining parameters on tool wear characteristics and component structural integrity and performance. However, testing the different permutations of metal removal parameters and tool combinations is expensive and time consuming at the development stage. The novel approach developed and presented here, enables the machining of smaller titanium parts that can be compared 1-to-1 to parts extracted from industrial machined disc components. This approach not only reduces cost, but ultimately accelerates the research and development process due to more rapid feedback between different iterations of the machining parameters.

The proposed technique specifically replicates the face turning operation performed in rotational critical titanium components, such as compressor discs, using small coupons machined in a standard CNC machining centre. The machined coupons can be fatigue tested through a 4-point bending and microstructural analysis can be performed on the tested coupons to directly study the effects of the machining process on the surface and underlying microstructure.