HR3C钢高温时效过程中的析出相

来源期刊：金属学报2010年第7期

论文作者：方园园 赵杰 李晓娜

文章页码：844 - 849

关键词：HR3C钢； 时效； 析出； 显微组织

Key words：HR3C steel； thermal aging； precipitation； microstructure

摘    要：本文研究了HR3C钢在750℃下时效500 h前后的显微组织变化和第二相的种类.研究结果表明,时效后HR3C钢中的析出物主要为形状各异的M₂₃C₆和NbCrN,其中M₂₃C₆在晶界和晶内均有析出,NbCrN以极其细微的尺寸大量弥散分布于晶内;时效过程中弥散析出的M₂₃C₆和极其细微的NbCrN提高了HR3C钢的硬度.晶内及晶界析出的M₂₃C₆晶格常数均为基体的3倍,并与基体保持完全共格的关系,晶界处部分M₂₃C₆转变成了高Cr的σ相.

Abstract: HR3C steel (Fe-25Cr-20Ni-Nb-N) is a new type of austenitic heat-resistant steel which has been widely used for super-heater and re-heater tubes in the ultra supercritical pressure (USC)boiler.The mechanical properties of HR3C steel were dependent on the stability of the microstructure, particularly the large amount of precipitates formed during service.This work was focused on the change of microstructure and the precipitations of HR3C steel after thermal aging for 500 h at 750℃.The results indicated that the major precipitates were variform M₂₃C₆ carbides and NbCrN nitrides.M₂₃C₆ carbides precipitated on grain boundaries and in intragranular.Fine and dispersed NbCrN nitrides were found to precipitate in intragranular.The hardness of HR3C steel had been improved through dispersed M₂₃C₆ and fine NbCrN precipitates after thermal aging for 500 h at 750℃.All the M₂₃C₆ carbides,with lattice parameter of three times of the austenite matrix,grown in a cube to cube orientation relationship with the matrix.Some of the M₂₃C₆ carbides which precipitated on grain boundaries were transformed into σ phase.