Residual Stress Analysis in PVD Coated Austempered Ductile Iron

Abstract

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.

Mechanical and tribological behavior of Ti/TiN and TiAl/TiAlN coated austempered ductile iron

“…The surface residual stresses of the coated samples are also compressive, with average values of 3.65 and 5.20 GPa for the Ti/TiN and TiAl/TiAlN samples, respectively. According to a previous work [22], the residual stresses of the coated samples are independent of the measurement direction indicating a rotationally symmetric stress state. An increase in the stress level by the addition of a third element in a binary coating has been previously reported by other authors [25][26][27][28].…”

“…The patterns of the bilayer TiAl/TiAlN coatings, Fig.2 (b [22], ADI residual stresses vary according to the measurement direction, being smaller perpendicular to the grinding marks. The Ra values of the coated samples are close to each other and are higher than the value of uncoated ADI due to the presence of macroparticles (protrusions) in the coatings [23,24].…”

Mechanical behavior of PVD coatings deposited on ADI

“…Moreover, the authors of the present work found a combination of industrial-use processing parameters producing PVD TiN and CrN coatings of acceptable characteristics as far as coating thickness, hardness, residual stresses and adhesion are concerned, causing no significant deterioration of ADI microstructure. Additionally, the analysis of the effects of the substrate characteristics on coating properties evidenced little influence of the austempering temperature and nodule count [12][13][14].…”

Multilayer Coating Formation at the Deposition from Plasma

“…The experimental results demonstrate that nanohardness is seriously affected by the residual stress [5]. Residual stresses depend on properties of substrates, surface finishing methods and processing parameters [6,7] It was shown that the residual stresses in the coatings deposited with ion assistance depend on the thickness of the coating and the flux and energy of the bombarding ions [8]. It was marked in [9] that residual stresses can arise from three sources: thermal, intrinsic and lattice mismatch.…”