PVD coatings are being developed that are expected to allow titanium aluminides, which offer very high strength to weight ratios, to be used at higher temperatures.
Gamma aluminide turbine blades based on Ti47Al2Cr2Ni, for example, have been shown to be as strong as nickel-based alloys up to 760ºC, while being only half the weight. But at the same time, wear and erosion resistance are compromised when the operating temperature exceeds 650ºC.
The project to further develop these materials is called Innovatial, and has 24 partners including the Nanotechnology Centre for Physical Vapour Deposition Research in the Materials and Engineering Research Institute at Sheffield Hallam University, which is looking at coatings.
Coating families already developed by the centre in Sheffield include TiAlYCrN, CrAlYN/CrN, CrN/NbN, TiAlN/VN, TiAlCN/VCN and Me/C, which offer greatly reduced friction, increased wear and corrosion resistance and good protection against high temperature oxidation. Most of these have already transferred to industrial applications such as cutting tools for dry, high-speed machining, parts for textile machines, metal forging and glass moulds.
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