Wear resistance of CVD and PVD multilayer coatings when dry cutting fiber reinforced polymers (FRP)

This work discusses the performance of multilayer coatings in dry cutting fiber reinforced polymers. The cutting tests were performed on unidirectional carbon/epoxy and glass/epoxy specimens with 45° fiber orientation using both Chemical Vapor Deposited (CVD) and Physical Vapor Deposited (PVD) multilayer coatings with neatly different composition, grain size and substrate-to-coating adherence. CVD TiCN/Al2O3/TiN with low adherence (CVD-L), PVD TiAlN/AlCrO with medium adherence (PVD-M) and PVD TiN/TiAlN with high adherence (PVD-H) inserts were considered for experimental tests. Scanning Electron Microscope (SEM) was utilized to characterize the flank wear patterns. The apparent friction coefficient dealing with the material removal process was deduced from cutting forces measured using Kistler piezoelectric dynamometer. The adhesive frictional signature was examined on both new and worn inserts through series of micro-scratch tests using Atomic Force Microscope (AFM). While abrasion mechanisms dominate the flank wear upon all inserts, the abrasion mode transforms from mild to severe depending upon coating layer characteristics. Regular inspections on the worn face demonstrated that the fail of first-deposited coating layer characterizes a threshold point from which the insert behavior drastically changes. The change in forces and friction tendencies' slopes beyond threshold proves that fiber phase abrasiveness dominates wear mechanisms irrespective to coating type.