Tribology in Industry (Jun 2012)
Vanadium Alloyed PVD CrAlN Coatings for Friction Reduction in Metal Forming Applications
Abstract
Hard coatings deposited on forming tools are used to improve the forming process and to increase tool life. The decrease of tool wear and reduction of friction are the main motivations for the development of self-lubricating coatings for forming applications at elevated temperatures. In the present study (Cr,Al,V)N (Physical Vapour Deposition) coatings with 5, 11 and 20 at % vanadium were deposited via a combination of HPPMS (High Power Pulse Magnetron Sputtering) technology and direct current (DC) Magnetron Sputter Ion Plating (MSIP) PVD. The hardness and Young’s Modulus of the coatings were investigated by nanoidentation. Furthermore, high temperature Pin-on-Disk (PoD) tribometer measurements against Ck15 (AISI 1015) were realized at different temperatures and compared with a (Cr,Al)N reference hard coating. The samples were analyzed by means of SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction) measurements after Pin-on-Disk (PoD) tests. Moreover TEM (Transmission Electron Microscopy) analyses were carried out after 4 h annealing at 800 °C in ambient air to investigate the diffusion of vanadium to the coating surface. The tribological results at 800 °C show no improvement of the friction coefficient for the pure (Cr,Al)N coating and for the layer with 5 at % V. A time-dependent decrease of the friction coefficient was achieved for the coatings with 11 at % V (µ=0.4) and 20 at % V (µ=0.4) at 800 °C.
