Oxidation Behavior of 2Cr12NiMoWV Steel in High-Temperature and High- Pressure Water Vapor

Abstract

Discrete mass gain method is adopted to determine the oxidation kinetic behaviors of 2Cr12NiMoWV steel in water vapor at 540°C and 17.5 MPa. Results indicate that the kinetic curve of the oxidation experiences a dramatic turning where the oxidation has lasted 20h, namely, the oxidation is faster than before the oxidation point of 20h, then oxidation rate is greatly reduced;, and after the oxidation has lasted for 300h, its reaction is inhibited to enter into a relatively stable period. The test analysis of oxide film under scanning electronic microscopy and electronic probe microanalyser shows that the formation process of the oxide film is as follows: needle-like oxide nuclei → short-strip oxide → fine equiaxed crystal grains → large equiaxed crystal grains or columnar crystal particles. The alloying elements involved in oxidation represent the law as follows: Fe, Mo and Si react with vapor at the initial stage of oxidation reaction to form Mo and Si-contained Fe-rich oxide. As the oxidation reaction proceeds, Cr gathered at the interface between the surface oxide film and the matrix, is internally oxidized. The Mo, Si and Cr in the surface oxide will be continuously volatilized with the occurrence of oxidation reaction.