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Systematic theoretical search for alloys with increased thermal stability for advanced hard coatings applications

H Lind , F Tasnádi and I. A. Abrikosov

New J. Phys. 15 095010 (2013)


Introduction and Background State-of-the-art hard coating materials gain much of their material properties through the formation of nanoscale crystal structures. In TiAlN, the limit of high temperature hardness is set by the transformation of cubic AlN phase into a wurtzite one which happens at around 900 ° С . In a previous work we showed that the alloying of small quantities of CrN allow the formation of a c-CrAlN phase that delays the onset of the detrimental wurtzite phase to higher temperatures.

The Main Results In this paper we present a systematic search for transition metals that if alloyed into AlN increases the stability of the cubic phase relative to the wurtzite. The criterion for our search is the difference in equilibrium enthalpy between the two phases and we perform our search across a wide range of transition metals. In this we show that group 6-9 transition metals improve the stability of the cubic phase the most with Fe breaking the trend.

Wider Implications The results presented here are to be considered as a guide to finding candidate materials worth further study using more in-depth computational techniques with the ultimate goal of finding new hard coating materials with good high temperature properties. We must remember however, that our results so far tell us nothing of solubility limits or overall stability, only relative stability of phases and that there is much work yet to be done before we can confirm our candidates as new functional materials.

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Last updated: 10/07/13