Chromium carbides melting temperatures

Tetrachromium Dicarbide, Cr C -— By melting chromium at temperatures above 1840° C. for fifteen minutes in a crucible of pure carbon, frequently stirring vith a carbon rod, alloys saturated with carbon are obtained. These contain no free chromium, but only carbide and graphite. On washing with hot 24 per cent, hydrochloric acid part of the alloy dissolves, and the ratio of chromium to carbon dissohing indicates that the soluble carbide has the composition Cr Cg, but the existence of this has not been confirmed by isolation. 

Interstitial nitrides are similar to interstitial carbides in structure and composition, and the two groups of materials closely resemble each other. The nitrides however are not as refractory. In fact, only the nitrides of Group IV and V have melting points above 1800°C. Those of Group VI, i.e., chromium, molybdenum, and tungsten nitrides, have lower melting (or decomposition) points and dissociate rapidly into N2 and the pure element at high temperature ( 1000"C). Their chemical stability is relatively poor and they do not therefore meet the refractory criteria. They are mentioned in this chapter for reference purposes. 

Nickel-based alloys, which form the bulk of alloys produced, are basically nickel-chrome alloys with a face-centered cubic solid-solution matrix containing carbides and the coherent intermetallic precipitate y-NijlAfTi). This latter precipitate provides most of the alloy strengthening and results in useful operating temperatures up to 90% of the start of melting. Further additions of aluminum, titanium, niobium, and tantalum are made to combine with nickel in the y phase, and additions of molybdenum, tungsten, and chromium strengthen the solid solution matrix. 

---