Rolling contact fatigue behavior of Ti/TiN coated ADI by cathodic arc deposition

D.A. COLOMBO; J.M. MASSONE; M.D. ECHEVERRÍA; A.B. MÁRQUEZ

CERAMICS INTERNATIONAL

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2017 vol. 43 p. 4263 - 4271

0272-8842

This workstudies the rolling contact fatigue (RCF) behavior of austempered ductile ironsamples coated with Ti/TiN by cathodic arc deposition. The influence of the TiNlayer thickness on the characteristics and RCF life of the coated samples isanalyzed. RCF tests were performed in a flat washer type testing rig, using athrust ball bearing as a counterpart. The maximum contact pressure was 1400MPa. RCF tests results were analyzed using the two-parameter Weibulldistribution. The rolling track of the tested samples was examined by using SEMand EDS.The resultsshow that the surface hardness, residual stresses and coating adhesion strengthof the samples increase as TiN layer thickness increases while surfaceroughness, coating hardness and elastic modulus do not vary significantly withthe TiN layer thickness. Regarding the RCF tests, two failure mechanisms wereobserved in the coated samples, coating delamination and substrate spalling.Coating delamination turned out to be the most predominant mechanism andoccurred at fewer loading cycles than substrate spalling. The EDS analysisrevealed that inside the delaminated areas the Ti interlayer remained adheredto the substrates in all the cases. Extended tests on delaminated samples showgrowing delamination until final failure by substrate spalling occurred. TheWeibull analysis indicates that the RCF life of the coated samples seems tohave a tendency to increase with the TiN layer thickness and, in the case ofthe thicker TiN layer, to exceed the life of uncoated ADI after the extendedtests. However, due to the number of samples employed, the statistic analysisdoes not show significant differences in the RCF behavior of the uncoated andcoated samples.