Anti-friction and wetting behavior of a new polymer composite coating towards aluminium and dry machining of AA2024 alloy by coated end mills

Soft coating materials now find increasing scopes of applications in environment friendly dry machining of difficult materials like aluminium and its alloys. A composite solid lubricant coating (Gr-X), having graphite and polytetrafluoroethylene (PTFE) as principal constituents, has been proposed to serve the purpose of arresting Built UP Edge (BUE) and Built Up Layer (BUL) in dry machining of aluminium. Its performance has been evaluated in depth in comparison to that of MoS2, which is a well-known solid lubricant. The chemical inertness and coefficient of friction of Gr-X were investigated in wettability and pin on disc test respectively. Compared to MoS2, Gr-X exhibited its less chemical affinity and coefficient of friction (especially at humid atmosphere) with aluminium. Further Gr-X was evaluated in end milling of AA2024 under dry environment, which promises green machining. BUE and BUL were completely eliminated by Gr-X coated tool, resulting in good surface finish and lower magnitude of cutting force. Summarily the proposed Gr-X coating can be a good and feasible economic solution in low Material Removal Rate (MRR) regime machining at low to medium range speeds, which also conforms to the norms of sustainability.