Oxidation behavior of vacuum plasma-sprayed hafnium–tantalum nitrides. Issue 19 (7th August 2015)

• Record Type: Journal Article
• Authors: Schulz, Bradford C.; Butts, Daniel; Thompson, Gregory B.
• Is Part Of: Journal of materials research. Volume 30:Issue 19(2015)
• Page Start: 2949
• Page End: 2957
• Publication Date: 2015-08-07
• Subjects: vacuum plasma spray, -- oxynitride scale, -- ultra high-temperature ceramics; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1557/jmr.2015.191
• Languages: English
• ISSNs: 0884-2914

Abstract

Abstract: Abstract : A series of (HfN)1− x (TaN) x, ceramics with x representing the starting powder blend compositions of 0.0, 18.8, 28.1, and 46.7 at.%, have been fabricated by vacuum plasma spraying. During the plasma spraying, the mixture lost approximately 25 at.% nitrogen facilitating the precipitation of metallic and metal-rich nitride phases. These specimens underwent static air oxidation exposure up to 1700 °C. In general, it was found that the addition of tantalum nitrides to the hafnium nitrides resulted in poorer oxidation behavior. However, the 18.8 at.% specimen deviated from this trend and had the lowest observed mass change. This specimen formed a dark-colored oxide scale, indexed as Hf6 Ta2 O17, which acted as a passivation layer. Within the scale, hafnium oxynitride phases were observed. A transformation pathway in forming these rhombohedral oxynitride phases is proposed by the filling in of oxygen in the light element interstitial locations of the rhombohedral ε-Hf3 N2 and ζ-Hf4 N3 structures.