回火温度对42CrMo高强钢应力腐蚀断裂行为的影响

EFFECT OF TEMPERING TEMPERATURE ON STRESS CORROSION CRACKING BEHAVIOR OF 42CrMo HIGH STRENGTH STEEL

研究了回火温度对高强度42CrMo 钢应力腐蚀断裂行为的影响。结果表明,在淬火态和低温回火态.均为沿晶断裂.K_(ISCC)很低;当回火温度高于300℃后,K_(ISSCC)随回火温度升高而显著早升,断裂方式从沿晶型过渡为穿晶韧窝和沿晶的混合型。俄歇能谱和电镜分析表明,该钢的应力腐蚀断裂行为主要决定于碳比物的分布。在淬火态和低温回火态,碳化物主要分布于原奥氏体晶界,导致沿晶断裂和 K_(ISCC)值很低。较高温度回火后,晶界上碳化物的聚集粗化和晶粒内部碳化物的大量析出,导致了断裂方式由沿晶型向混合型转化和 K_(ISCC)的明显升高。

The effect of tempering temperature on the stress corrosion cracking behavior of 42CrMo high strength steel in 3.5% NaCl aqueous solution has been studied with Auger electron spectroscopy,electron microscopy and fracture mechanics method.Results show that,in the quenched and low temperature tempered conditions,42CrMo steel has very low K_(ISCC) and fractures intergranularly.With the rise of tempering temperature from 300℃ to 500℃.K_(ISCC) increases apparently and the fractography changes from intergranu- lar mode to a mixture of transgranular dimpled rupture and intergranular mode.Analyses show that the stress corrosion cracking behavior is mainly controlled by the distribution of carbide.In the quenched and low temperature tempered conditions,preddominant distribu- tion of carbide along prior austenitic grain boundaries is the main cause leading to inter- granular fracture and very low K_(ISCC).In high temperature tempered conditions,the com- bined effects of the coarsening of the carbide along the grain boundaries and the precipita- tion of much carbide within grains result in the apparent increase of K_(ISCC) and the change of fractography from intergranular to mixed mode.