Residual Stresses on Various PVD Hard Coatings on Tube and Plate Substrates

Harri Lille,Alexander Ryabchikov,Fjodor Sergejev,Priidu Peetsalu,Liina Lind,Jakob Kübarsepp,Valdek Mikli

doi:10.3390/coatings10111054

Harri Lille, Alexander Ryabchikov + Show 5 more

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https://doi.org/10.3390/coatings10111054

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Abstract

In this study, the average residual stresses were determined in hard PVD nACRo (nc-AlCrN/a-Si3N4), nACo (nc-AlTiN/a-Si3N4), AlCrN, TiAlN, and TiCN commercial coatings through the deflection of the plate substrates and the simultaneous measurement of length variation in thin-walled tubular substrates. The length measuring unit was used for the measurement of any length change in the tubular substrate. A change in tube length was reduced to the deflection of the middle cross-section of the elastic element for which deformation was measured using four strain gauges. The cross-sectional microstructure and thickness of the coatings were investigated by means of scanning electron microscopy (SEM), and a determination was made of the chemical composition of the coatings and substrate by means of energy dispersive X-ray spectroscopy (EDS). The values of average compressive residual stresses, as determined by both methods, were very high (with a variation of between 2.05 and 6.63 GPa), irrespective of coating thickness, but were dependent upon the shape of the substrate and on its position in relation to the axis of the rotating cathode. The thicknesses of the coatings that were deposited on the plates with two parallel fixings (such as the nACRo coatings on the front surface at 6.8 μm and on the rear surface at 2.9 μm) and on the tubular substrates (10.0 μm) were significantly different. The higher average compressive residual stresses in the coating correlate to the higher average relative wear resistance that was obtained during field wear testing.

Highlights

Physical Vapor Deposition (PVD) coatings are used inter alia for blanking, punching, and cutting applications [1] and can be deposited both on plain surfaces and more complex ones [2,3]
The average residual stresses in various PVD hard coatings on tube and plate substrates were calculated using as an experimental parameter, along with the length variation of the tube, and the deflection of the plate
The calculated average values of residual stresses were compressive and high, varying from 2.05 to 6.63 GPa, and were of the same range as the corresponding data shown in the available literature that were obtained by the X-ray technique

Summary

Introduction

Physical Vapor Deposition (PVD) coatings are used inter alia for blanking, punching, and cutting applications [1] and can be deposited both on plain surfaces and more complex ones [2,3]. It is well known that residual stresses that arise in coatings during the deposition process [1,4,5] have an important effect on the service life of the coating by means of influencing its mechanical and tribological properties and adhesion [6]. Residual macro- and microstresses in materials can be distinguished. Macrostresses (average values), as Type I, vary within a bulk coating, and microstresses, as Type II, operate at the grain-sized level [7,8]. It should be noted that the (micro) residual stresses that have been measured by X-ray diffraction are the arithmetic average stress results in the small irradiated area alone.

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