Effect of carbon addition on tribological performance of TiSiN coatings produced by cathodic arc physical vapour deposition

Abstract

Effect of carbon addition on tribological behaviour of multilayered TiSiN coating was investigated and the performance of TiSiCN and TiSiN coatings on cold forming steel dies were compared. The coatings were deposited by an industrial cathodic arc physical vapour deposition process. Surface analysis by X-ray diffraction and micro-Raman spectroscopy revealed that structure of TiSiN was mainly composed of TiN crystallites together with a silicon-rich amorphous phase. In the case of TiSiCN coating, presence of Ti(C, N) crystallites, graphite and amorphous carbon were identified. Both coatings contained high compressive residual stresses, as measured by sin2ψ method. Nanoindentation testing showed hardness values of 25 GPa and 29 GPa for TiSiN and TiSiCN, respectively. Tribological tests, conducted on a ball-on-disc wear tester using zirconia ball, indicated lower coefficient of friction of the coatings as compared to the steel substrate; the lowest value of 0.2 was experienced by TiSiCN coated surface. Study of wear mechanisms proved that application of coatings changed the prevailing wear mode from adhesive to abrasive, decreasing the wear rate to one third. Addition of carbon to TiSiN changed tribological behaviour of the coating, similar to a self-lubricant film. Field tests of TiSiCN coating on forming dies, for deep drawing operation of steel tubes, revealed 10 times increase of die lifetime.