Accuracy of truncated Leiden and Berlin virial expansions for pure gases and sealing joints between silicon carbide and stainless steel

Abstract

Pure gases such as methane, carbon dioxide and steam were used to make comparisons between Leiden and Berlin virial expansions for the calculation of the compressibility factor, fugacity coefficient and enthalpy residual. Results show that the Leiden expansion is better than the Berlin expansion with truncation after the second virial coefficient for both expansions, and also with truncation after the third virial coefficient for both expansions. Also, joining techniques to join silicon carbide to steel were studied. Brazing is the technique more used, and several active filler metals such as Ag-Cu-In-Ti, Ag-Cu-Ti, plus carbon fibers Ag-Cu-Hf and Niobium were used. This review shows that the strength of the joint is affected by the amount of active filler metal in the alloy, heating element and atmosphere, composition and surface of SiC, thickness of the joint, and time. In general, brazing temperature is limited by the melting point of the filler metals, which is generally below 1000 ⁰C. An alternative to overcome this problem in brazing is using a functionally graded material (FGM) that is formed with the native elements. This FGM has one end of almost 100% stainless steel, which is joined using very well known processes of joining metals. The other end of the FGM, which is almost 100% SiC, is joined using a reaction-forming method that produces an interlayer of SiC plus Si and supports temperatures as high as 1350 ⁰C.