Microstructure and mechanical and tribological properties of a lubricant coating for incremental forming of a TI sheet

Abstract

Due to galling with other materials, Ti and its alloys call for solid lubricants during forming. Deforming Ti sheet becomes even more difficult when the forming process involves very low contact area, such as in the novel process single point incremental forming (SPIF). Retaining lubricant at the tool/sheet interface while performing local deformation, as in SPIF, has always been a challenge. One way to satisfy this challenge is to develop a porous surface coating on the sheet and fill its pores with lubricant particles. For SPIF, an electro-chemical deposition process called micro-arc oxidation (MAO) has shown promise to fabricate coatings of desired pore size and thickness to fulfill the said objective. In the present work, the characterization of an MAO coating has been carried out to clarify its role during the incremental forming of pure Ti sheet. The results regarding hardness, bond strength, XRD microstructure and friction co-efficient of the coating under various lubrication conditions are reported.