The Influence of Long-term Ageing on the Microstructure of Sanicro 25 Steel

Abstract

Sanicro 25 (22Cr25NiWCoCu) is a newly developed austenitic stainless steel used in the boiler pressure superheaters and reheaters with ultra-supercritical high-efficient parameters. The paper presents the results of microstructure testing and secondary phase separation processes after 20,000 h ageing at 700 and 750 °C. In the initial stage of ageing, the precipitation of numerous very small M23C6 chromium carbides and Laves phase were observed. The long-term ageing related to temperature revealed the existence of secondary phases: M23C6, MX, NbCrN, Laves phase and  phase. The test results presented in the paper are part of the developed material characteristics to be used for predicting the service life of the material of components operated under creep conditions.

Microstructure, macro-, and nano-hardness assessment of AISI 302 steel aged at 1000°C

“…At the level of scientific research, an attention has been paid to the assessment of the metallurgical behavior of the stainless steels, including their aging behavior [5][6][7][8][9]. At hightemperatures and for prolonged holding times, several studies demonstrated that the microstructure of the austenitic stainless steels undergoes changes as the increase of the grain size and the decrease in the area of grain boundaries per unit volume [10][11][12][13].…”