Enhanced sulphidation/oxidation resistance of Ti–45Al–8Nb alloy by nanostructured CrAlYN/CrN coatings at 750 °C

Abstract

This paper discusses the sulphidation/oxidation protection offered by multilayer CrAlYN/CrN coatings etched by Cr, CrAl and Y ions, deposited by a combined high power impulse magnetron sputtering (HIPIMS)/unbalanced magnetron sputtering (UBM) technique on a Ti–45Al–8Nb alloy (at%). The test was performed at 750 °C in an environment of H2/H2S/H2O yielding low oxygen (10−18 Pa) and high sulphur (10−1 Pa) partial pressures for up to 1000 h. The results show that all the exposed materials underwent uneven degradation; some places developed a thin protective oxide scale (Al,Cr)2O3 with a tiny sulphur content, whilst others developed a porous non‐protective TiO2 + Al2O3 scale as well with a tiny sulphur content.

The corrosion behavior of a sputtered micrograin film on Fe-5Cr-5Si alloy in H 2 -CO 2 -H 2 S mixture at 700 °C

“…For example, Bamba [13] and Guo [14] reported that the addition of Cr to Fe-Si alloy can induce the formation of SiO2 layer in pure oxidizing atmosphere. Second, we also could decrease the grain size of the alloy to improve the outward diffusion of the Cr and Si to achieve the selective oxidation of Si and form the protective scale [11,12]. In our previous study, the Fe-Si alloy exhibited poor corrosion resistance in the H2-CO2-H2S at 700 o C [3], which is not acceptable.…”

“…The preparation of a protective coating on the surface of the alloy is a favorable way to improve the corrosion resistance of the substrate. Dudziak et al [11] reported that multilayer CrAlYN/CrN coatings could induce a protective layer locally on Ti-45Al-8Nb in H2/H2S/H2O mixture. Besides, Nano-or micro-coating is reported to be able to improve the oxidation/sulphidation resistance of the alloy [12].…”

Air oxidation behaviour of standard PVD and novel HIPIMS coatings at 750°C for 1000 h

“…9 The introduction of Al into the face centred cubic (FCC) CrN structure was found to significantly improve the oxidation resistance due to the formation of a protective Al rich oxide layer that reduces O diffusion into the main coating. 10 The oxidation sulphidation resistance of these coatings was recently investigated by Dudziak et al, 11 the research showed that multilayered coatings suffer due to the formation of microcracks in the deposited coating, where Ti and Al diffuse outwards to form a standard multi-layered oxide scale consisting of an Al 2 O 3 -TiO 2 mixture. This paper shows the results of air oxidation of the standard TiAlCr and Al 2 Au coatings produced by means of PVD systems and PVD systems based on HIPIMS technology.…”

Effects of Cr Addition and a Magnetron Sputtered Film on the Oxidation-Sulfidation Behavior of Fe-xCr-5Si Alloys in H2-CO2-H2S Mixture at 800°C

“…[19][20][21] However, the corrosion resistance of sputtered films has not been observed in either pure suphidizing atmospheres [22][23][24] or in atmospheres of low oxygen and high sulfur pressures. 25 The present paper examines both the TEE of chromium on the oxidation-sulfidation behavior of Fe-5Si alloy and the effect of the z E-mail: sliu12s@imr.ac.cn deposition of a Fe-5Cr-5Si film by magnetron sputtering on the oxidation-sulfidation behavior of a cast Fe-5Cr-5Si alloy in an atmosphere with a low oxygen pressure and a relatively high sulfur pressure. Based on the analysis of the mechanism of formation of the scale on coated Fe-5Cr-5Si, the critical concentrations of chromium and silicon needed to form a protective oxide layer at the film/alloy interface are evaluated.…”