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This work studied the sliding wear performance of TiAl-based nitride coatings synthesized on austempered ductile iron (ADI) by cathodic arc deposition (CAD) and plasma-based ion implantation and deposition (PBIID). Monolayer CAD TiAlN films and bilayer CAD and PBIID TiAl/TiAlN films deposited on an experimental device were analyzed and benchmarked against a commercial bilayer CAD film. Sliding wear was evaluated in a pin–on–disc tribometer. Two test conditions were employed, one intended to prevent damage (low load, short distance) and another intended to promote damage (higher load, longer distance). Regarding low load tests, all coated samples showed friction coefficients of 0.40–0.45 and negligible wear. Regarding high load tests, all coated variants exhibited lower or equal disc and pin wear rates with respect to uncoated ADI. In addition, coated samples displayed steady-state friction coefficients between 0.2 and 0.6 while uncoated ADI steady-state coefficients between 0.6 and 0.85. [ABSTRACT FROM AUTHOR]

Abstract This work studies the surface characteristics and, particularly, the rolling contact fatigue (RCF) behavior of austempered ductile iron (ADI) samples coated with TiN based coatings of about 1 μm in thickness. Films synthesized by cathodic arc deposition (CAD) at a fixed nitrogen flow, compositional gradient films synthesized by CAD at a variable nitrogen flow and plasma based ion implanted and deposited (PBIID) films were comparatively analyzed. The results indicated that CAD films showed a strong TiN (111) preferred orientation while PBIID films a more randomly orientation. The crystallite size of CAD films was more than the double of PBIID films. Residual stresses of the PBIID films were lower than those of CAD films, the lowest hardness and elastic modulus were obtained for CAD films grown at variable nitrogen flow, while no significant differences in roughness, H/E ratio and adhesion were observed among the different films. Regarding RCF tests, failures in samples coated with TiN at constant flow were characterized by a progressive coating delamination followed by the formation of fatigue spalls inside the delaminated areas. Failures in samples coated with PBIID and gradient TiN were characterized by the formation of fatigue spalls with slight coating delamination. There were no significant differences between the RCF resistance of uncoated ADI and the samples with CAD films while the samples with PBIID films had a noticeably higher resistance. The better performance could be associated with the low compressive residual stresses and the fine grained microstructure induced by the PBIID process. Highlights • Cathodic arc deposited (CAD) films synthesized at variable and constant nitrogen flows. • Constant-flow CAD films delaminated during rolling contact fatigue (RCF) tests. • Neither variable-flow CAD nor ion-implanted/deposited films delaminated during RCF tests. • RCF behavior of austempered ductile iron was not modified by CAD. • RCF endurance of austempered ductile iron increased by ion-implanted/deposited films. [ABSTRACT FROM AUTHOR]