Residual stress, surface defects and corrosion resistance of CrN hard coatings1
Introduction
Filled and fibre reinforced plastics are increasingly applied during plastic manufacturing. These materials cause, by combined abrasive and corrosive attack of hard fibres and F, S, Cl from plastic decomposition, respectively, a substantial reduction of the lifetime of machinery, dies and moulds [1].
Hard coatings of metal nitrides such as CrN have proven their capability to increase tool lifetime not only during abrasive action of hard materials but also in many chemically aggressive environments [2]. These hard coatings are generally deposited by physical vapour deposition (PVD) deposition techniques. The microstructure of PVD coatings is characterized by a columnar microstructure and local surface defects. Corrosive problems during use hard generally attributed to voids between these columns, to pinholes and to eventually existing cracks. Local corrosion may appear on those sites and cause an accelerated degradation of the metallic substrate. The appearance of defects in coatings is closely related to residual coating stress. The study of the residual stress of these nitride hard coatings and the relationship of this parameter with the deposition conditions and corrosion performance is therefore very interesting. Another important parameter for the protective capabilities of coatings is the density of large defects which is revealed by optical microscopy.
The relationship of the residual stress and corrosion resistance will be the object of further studies.
Section snippets
Film deposition
The CrN coatings were deposited onto mechanically polished stainless steel (AISI 316), 0.5 mm thick, by RF reactive magnetron sputtering. The average surface roughness before and after the coating deposition was ca 0.3 μm. Before coating deposition, the substrates were ultrasonically cleaned and, in situ, RF sputter etched in a pure Argon atmosphere to remove the native oxide scale. Subsequently, a thin pure Cr metal interlayer (ca 100 nm) was deposited to improve the corrosion resistance 3, 4.
Residual stress and microstructure
All Chromium nitride coatings showed that a Cr:N ratio of 1:1 as determined by RBS measurements. XRD revealed single phased thin films with a strong texture ([111] direction normal on sample surface) for all coatings. Nevertheless, some traces of [200] phase can be detected. To distinguish the [200]-XRD peak from the signals resulting from the metallic substrate, the peaks were fitted by Gaussian functions (see Fig. 1(b)). The so obtained [200] peak intensity (I200) can be compared to the
Conclusions
Within the light of this article our findings can be summarized as follows:
- 1.
CrN coatings produced by RF magnetron sputtering with a DC or RF bias applied to the stainless steel substrates are fine grained and present a strong [111] texture. Nevertheless, crystals with [200] planes parallel to the substrate surface can be found also but in a relatively low percentage (<14%).
- 2.
Generally the coatings were in a state of strong compressive stress (ca −1 to −5 GPa, depending on substrate bias). This
Acknowledgements
The authors gratefully acknowledge the image analysis by Mr M. Filipe Costa and the grain size analysis of the XRD data by Dr Luis Rebouta, both from the Physics Department of the Universidade do Minho.
References (11)
- et al.
Mater. Sci. Eng. A
(1991) - et al.
Mater. Sci. Eng. A
(1991) - et al.
Thin Solid Films
(1992) - et al.
Thin Solid Films
(1998) - et al.
Surf. Coatings Technol.
(1995)
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- 1
Presented at the ICAM '97/EMRS '97 Conference (Symposium K), Strasbourg, France, June 1997.