INFINA (EX INFIP)   05545
INSTITUTO DE FISICA INTERDISCIPLINARIA Y APLICADA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Wear behavior of bilayer Ti/TiN coatings deposited by cathodic arc deposition and plasma based ion implantation and deposition (PBII&D) on ADI
Autor/es:
JUAN PABLO QUINTANA; ADRIANA B. MÁRQUEZ; JUAN M. MASSONE; MARÍA D. ECHEVERRÍA; DIEGO A. COLOMBO
Lugar:
Shanghai
Reunión:
Conferencia; 14th International Conference on Plasma Based Ion Implantation & Deposition; 2017
Resumen:
Introduction: Austempered ductile iron (ADI) is commonly used for the manufacturing of mechanical components subjected to rolling or rolling/sliding contacts, such as gears and cams. A major cause of failure in this type of components is rolling contact fatigue (RCF). Hard coatings are widely used to improve hardness, wear resistance and corrosion resistance of a variety of metals, including ADI [1-5]. In previous works we studied the RCF behavior of ADI samples coated with hard coatings deposited by cathodic arc deposition (CAD) [6, 7]. It was found that the RCF resistance of the coated samples increases as coating hardness and film thickness decrease. In addition, it was observed that graphite nodules present on the substrate surface act as preferential sites for coating delamination due to large mismatch in mechanical properties between coatings and graphite nodules. This sharp interface could be eliminated by introducing the concept of functionally gradient materials (FGM) in the design of the coating [8]. Plasma-based ion implantation and deposition (PBII&D) could be another method to improve the RCF behavior of coated ADI. Materials and Methods: High resistance ADI samples were prepared following conventional practices of melting, casting, heat treatment and machining. The coatings were synthesized using an experimental DC cathodic arc system. Compositional gradient (GC) Ti/TiN films were synthesized by gradually varying the nitrogen flow during deposition. Hybrid (HY) Ti/TiN films were synthesized by the PBII&D method using a combination of CAD and plasma immersion ion implantation. Constant composition (CC) Ti/TiN films were synthesized by using a constant nitrogen flow during TiN deposition. Film thickness, existing phases, preferred orientation, surface roughness, hardness, elastic modulus, residual stresses and adhesion of each coating variant were determined. RCF tests were performed in a flat washer type testing rig using lubricated, pure rolling conditions. The maximum contact pressure (p0) was set at 1400 MPa. The rolling track of the samples was examined by SEM and EDS. RCF results were analyzed using the two-parameter Weibull distribution. Results and Discussion: The results indicate that films synthesized using conventional CAD showed a TiN (111) preferred orientation while those synthesized using PBII&D showed a (200) preferred orientation. No differences in surface roughness and adhesion were observed for the different coating variants. Hardness and elastic modulus of the hybrid films was similar to those of constant composition and higher than those of gradient composition. Residual stresses of the hybrid films were lower than those of gradient and constant composition. Regarding RCF tests, failures in samples with constant composition films were characterized by a progressive coating delamination followed by the formation of fatigue spalls inside the delaminated areas. Failures in samples with hybrid and gradient films 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 gradient and constant composition films while the samples with hybrid films have a higher resistance. Figure 1 shows the Wiebull plot for the uncoated and coated samples considering only fatigue spalls as failures. Conclusion: The application of compositional gradient and constant composition Ti/TiN films by conventional CAD does not modify the RCF behavior of ADI samples. On the other hand, the application of hybrid Ti/TiN films by PBII&D improves the RCF behavior of ADI samples, reaching double the life estimates.References: [1] H. P. Feng, S. C. Lee, C. H. Hsu, J. M. Ho, Study of high cycle fatigue of PVD surface?modified austempered ductile iron, Mater. Chem. Phys. 59 (1999) 154-161.[2] C.-H. Hsu, J.-K. Lu, K.-L. Lai, M.-L. Chen, Erosion and corrosion behaviors of ADI deposited TiN/TiAlN coatings by cathodic arc evaporation, Materials Transactions 46 (2005) 1417-1424.[3] C.-H. Hsu, K.-L. Chen, J.-H. Lu, Effects of electroless nickel interlayer on surface properties of CrN arc-coated austempered ductile iron, Surf. Coat. Technol. 203 (2008) 868-871.[4] C. H. Hsu, K. L. Chen, K. C. Lu, Effects of low?temperature duplex coatings on the abrasive and erosive behavior of ADI, Thin Solid Films 519 (2011) 4855-4859.[5] C.-H. Hsu, K.-H. Huang, Y.-T. Chen, W.-Y. 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