Influencia del espesor de película en la resistencia a la fatiga de contacto por rodadura de ADI recubierta con TiN mediante PVD

RE, N; D. COLOMBO; J. MASSONE; M. ECHEVERRÍA

Santa Fé

Congreso; Congreso SAM-CONAMET-IBEROMAT; 2014

SAM

This work studies the influence of the film thickness on the rolling contact fatigue (RCF) behavior of PVD TiN coated ADI samples. In order to obtain high resistance ADI, the samples were austempered at 280 ºC. Finally, the ADI samples were surface finished by grinding. Coatings were applied in an industrial reactor using processing parameters specifically selected for ADI. Deposition times were adjusted in order to obtain three different film thicknesses. RCF tests were performed in a flat washer type testing rig, using a thrust ball bearing as a counterpart. The maximum contact pressure was set at 1400 MPa. RCF tests results were analyzed using the two-parameter Weibull distribution. The rolling track of the tested samples was examined by using optical microscopy. The results obtained indicate that the coatings have thicknesses of about 0.7, 1.4 and 2.5 μm. Arithmetic average roughness, Knoop hardness and residual stresses of the coated samples increase as the film thickness increases. The adhesion strength quality of the coatings can be classified as HF1, according to the VDI 3198 standard. The adhesion strength does not vary with film thickness. Regarding the RCF behavior, it is observed that the resistance of the coated samples increases as film thickness decreases. Coatings with thinner film thickness extend the RCF life of ADI by 25% approximately, while coatings with intermediate and thicker film thickness reduce the RCF life of ADI. Failures in coated samples with thinner film thickness are characterized exclusively by pit formation in the substrate, while in coated samples with intermediate and thicker film thickness the dominant mechanism is the coating delamination.