【摘要】 通过SEM断口分析、TEM选区电子衍射及金相技术对汽轮发电机组25Cr2MoIV钢高温紧固螺栓脆化机理进行了研究。认为螺栓在高温工作条件下,晶内会出现大量与基体保持Baker Nutting关系的超微细析出物VC,使基体的硬度值由于共格强化及弥散强化而升高,而晶界不连续网状碳化物的析出,使邻近区域的合金元素贫化,造成晶界弱化是脆化失效的主要原因。经950℃高温正火加650℃回火能有效地消除脆化的微观组织因素,使材料重新具备良好的性能。更多还原

【Abstract】 The embrittlement mechanism of 25Cr2Mo1V high temperature fastening bolts used on turbogenerators has been studied. Analyses on fracture with SEM, SAED with TEM and metallography have been carried out. The results show that after working at high temperature for some time a great number of ultramicro carbides deposit in the grains. These precipitate, which keep Baker—Nutting relation with the matrix, will increase the hardness of the the matrix by coherent strengthening and dispersion strengthening,at the same time uncontinuous carbide networks deposit along the grain boundary and alloy elements of the areas around will decrease, thus the grain boundaries are weakened,this is the main reason for the brittle failure. Normalizing at 950℃ and tempering at 650℃ will eliminate the embrittlement microstructure and bring satisfied properties to the steel again.更多还原