AP-CVD ZrB2 process development for discrete and duplex UHTC coatings

Conference Dates

September 17-20, 2017


Refractory borides are a class materials with properties ideally suited to extreme operating conditions such as leading edges, spaceplanes, hypersonic vehicles and volumetric solar power receivers. The ability to coat complex geometries and varying materials with refractory borides such as zirconium diboride, (ZrB2), is offered through chemical vapour deposition, (CVD), methods. CVD ZrB2 can offer high purity, uniform and fully dense coatings economically, negating many of the current issues with powder processing methods that dominate commercial availability.

The study was conducted to establish ZrB2 coating processes by atmospheric pressure CVD, (AP-CVD), on a variety of substrate materials including graphite, CMCs, SiC coated CMCs, and C and SiC fibre fabric. Single layer coatings were developed, although these are limited in temperature performance, as well as multilayer ZrB2-SiC coatings to offer an innovative and effective solution to operation in the high and ultra-high temperature regimes. Literature studies demonstrated CVD processes could be achieved through direct chlorination of zirconium metal to generate a metal chloride precursor that underwent subsequent reduction with BCl3 and H2 to generate ZrB2 coatings. An iterative process of parameter selection and modification, deposition trials and analysis was undertaken to evaluate optimal deposition conditions.

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