| As ASTM T/P92 steel possesses high creep rupture strength and good high temperature strength,it was widely used in boiler steel to replace T/P91. T/P92 was applied in superhaeter and reheater pipes at a steam temperature of 600℃ extensively.Due to the operation features of Ultra Supercritical Pressure Boilers,the influence of degeneration of microstructure and properties of high temperature and pressure metal components during long service., the monitoring and rapid analysis at the working condition for the crucial high temperature and pressure metal components should be reinforced, which played the key role for guaranteeing the stable working order of Power Grid, reducing the negative influence on Power Grid safty because of disorderly closedown incident, improving the availability ratio of Ultra Supercritical Pressure Boilers, assuring the safe and stable operation of Ultra Supercritical Pressure Boilers, promoting and monitoring the uncertain factors resistance of Power Grid.In this paper, the different time and different high temperature aging tests of T92 heat-resistant matensite steel which was applied in Ultra Supercritical Pressure Boilers, were operated, the microstructure, the micro-chemical composition, the microhardness were analysised and tested;the precipitation,growth and transformation of the key phase( Laves-phases) in long run were studied and confirmed; the microstructure transformation, the mechanical properties change during the aging and creeps as well as the relationship between them are analysed; relationship between the material properties and microstructure and sevice life assessment of T/P92 steels were researched.The analysis results show : the longer the aging time,the carbides precipitated more on the grain boundary,the depletion of the alloy elements of the solid solution was more serious, grain coarsening was more serious, the microstructure degraded constantly. At the temperature of 700℃,Laves phase coarsened more quickly. The aggregation and growing up of carbides and Laves phase, the diffusion of the alloy elements in the matrix would lead to the degradation of the fracture toughness and high-temperature creep strength of T92 steel. It was difficult to ensure the safe operation of the Ultra Supercritical Pressure Boilers if T92 steel worked at 700℃ with long term. The service life would deteriorate because of overtemperature work. |
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