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This work studies the sliding wear behavior of PVD coated austempered ductile iron samples. The effects of the substrate surface finishing method (grinding and polishing) and coating material (CrN and TiN) on the wear behavior are evaluated. Coatings were applied in an industrial reactor. Deposition times were adjusted to obtain similar film thicknesses in both coating materials. Wear tests under dry sliding conditions were carried out with a pin-on-disc tribometer (ASTM G99). The steady-state friction coefficient and wear rate were calculated for each sample variant. The wear track of the discs was examined by using optical microscopy and stylus profilometry.The results obtained indicate that the uncoated and TiN coated samples show steady-state friction coefficients close to 0.8, while the CrN coated samples show steady-state values close to 0.4. The sliding wear tests do not produce the fracture and/or delamination of the films in any case. The specific wear rate of the CrN and TiN coated samples is close to zero, while that of the uncoated samples is higher. The wear rate of the uncoated samples is slightly higher for the ground ones. The specific wear rate of the pins (AISI 52100 bearing balls) is higher than that of the discs in all the cases. The wear rate of the pins tested against uncoated samples is higher for the ground ones. The wear rate of the pins tested against coated samples is higher for the polished and TiN coated ones.

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This work studies the influence of the PVD processing parameters on the characteristics of TiN and CrN coatings deposited on ADI substrates, austempered at 360°C, with different nodule counts and surface roughnesses. Coatings were applied by arc ion plating using an industrial reactor and different sets of parameters, with BIAS voltages, arc currents, chamber pressures and substrate temperatures varying from -100 to -250 V, 60 to 65 A, 0.7 to 2.8 Pa and 280 to 450°C, respectively. The effect of the different depositions conditions on the substrates microstructure was also analyzed. The existing phases, preferred orientation, surface topography, film thickness, hardness and adhesion of each coating were determined. The retained austenite content and hardness of each substrate were computed before and after coating deposition.The results obtained indicate that the different deposition conditions and coating materials evaluated do not generate significant changes neither in the resulting topography nor in the coating adhesion, which can be related to indices between HF1 and HF2. Coating adhesion was not affected by different substrate roughnesses. The combined reduction of BIAS voltage, arc current and chamber pressure leads to a decrease of TiN growth rate and hardness, while high substrate temperatures promotes an increase in TiN and CrN growth rates. Substrate temperatures around 300°C with deposition times of up to 240 min do not promote noticeable changes on the ausferritic microstructure, while temperatures of 400°C and above translate into a clear microstructural deterioration, even for short deposition times.

The aim of this work is to study residual stresses (RS) in PVD TiN and CrN coated ADI substrates with different nodule counts, austempering temperatures and surface finishing methods (grinding and polishing). Coatings were applied by arc ion plating using an industrial reactor and different sets of processing parameters. Residual stress measurements were performed by x-ray diffraction using the sin 2 ψ method along two principal axes on the samples surface (parallel and perpendicular to the substrate abrasion direction). The film thickness, hardness and adhesion of each coated sample were also evaluated.The results obtained indicate that RS in TiN and CrN coated samples are compressive irrespective of the different substrates, surface finishing methods and processing parameters utilized. The parallel and perpendicular RS do not vary significantly, indicating a rotationally symmetric biaxial stress state. The RS of the coated samples are not influenced by the different substrate characteristics regarding microstructure, hardness and surface roughness. The microhardness and RS of TiN and CrN coated samples increase with film thickness. The increase in substrate temperature together with the decrease in the values of BIAS voltage, arc current and chamber pressure lead to microhardness and RS reduction. Grinding produces surface hardening and reduction of the compressive RS in the substrates, but causes no variations in the RS of the TiN and CrN coated samples. The adhesion strength quality of TiN and CrN coatings to ADI substrates can be related to indices ranging from HF1 to HF2.