长时高温运行后1Cr18Ni12Ti奥氏体钢组织变化

Microstructure Variation of 1Cr18Ni12Ti Austenite Stainless Steel After Long-Time Operating at High Temperature

采用金相显微镜、扫描电镜和X射线衍射仪对1Cr18Ni12Ti奥氏体不锈钢管断口和显微组织中的析出相进行了分析,研究了导致材料脆化的原因、晶界和晶内析出相的结构以及析出相对材料性能的影响。结果表明,1Cr18Ni12Ti奥氏体不锈钢脆化是由于材料发生过时效,组织结构发生劣化的结果,主要表现为晶界出现连续和封闭的碳化物析出相,晶内析出针状σ相。这种组织结构的出现一方面阻止位错的运动和破坏变形的连续性,也使晶界附近组织贫铬化,导致材料的韧性、抗氧化和腐蚀性、甚至强度和高温持久性能下降。

The precipitates in the microstructure and the fracture of 1Cr18Ni12Ti austenite stainless steel tube were ana- lyzed by optical microscope, SEM and X-ray diffraction instrument. The causes of the steel brittleness, the structure of precipitate in the crystal and along the crystal boundary, and the influence of the precipitate on the performance of the steel were investigated. The results show that the brittleness of the 1Cr18Ni12Ti austenite stainless steel is caused by overaging happened with bad structural variation. Such variation are presented carbides precipitated along the crystal boundary and the acicular σ phase in the crystal. This structure inhibits the movement of dislocation and destroies the continuity of transmutation. On the other hand, it makes Cr poor alongside crystal boundary, which leads to decreasing the toughness, oxidation-resistance, erosion-resistance, and even the strength and high-temperature endurance properties.