V+Ti微合金化Mn-Cr系贝氏体型非调质钢的氢脆敏感性

Hydrogen embrittlement of V+Ti microalloyed Mn-Cr bainitic forging steel

利用电化学预充氢、慢应变速率拉伸和氢热分析试验,结合SEM、TEM及EBSD微观组织分析,对比研究了一种V+Ti微合金化Mn-Cr系贝氏体型非调质钢在锻态和500℃回火态的氢逸出行为及氢脆敏感性。结果表明,具有粒状贝氏体组织的锻态试样经500℃处理后块状M/A组元分解,并析出纳米级细小的(V,Ti)(C,N)和渗碳体,这使得回火态试样的抗拉强度降低而屈服强度显著提高。锻态和回火态试样预充氢吸附的氢主要为可扩散性氢,回火态试样中吸附的氢含量略低于锻态试样。以相对缺口抗拉强度降低表征的氢脆敏感性指数由锻态试样的31.8%降低为回火态试样的12.8%,500℃回火处理引起的微观组织变化是回火态试样具有优异抗氢脆性能的主要原因。

Hydrogen desorption and hydrogen embrittlement(HE)behavior of a V+Ti microalloyed Mn-Cr bainitic forging steel in the as-forged and 500℃ tempered conditions were studied by using electrochemical pre-hydrogen-charging,hydrogen thermal analysis(TDA)and slow strain rate tensile(SSRT)testing combined with SEM,TEM and EBSD microstructural analyses.The results show that the blocky martensite/austenite(M/A)constituents decompose with the precipitation of nano-sized(V,Ti)(C,N)and cementite particles,which causes a decrease of tensile strength while a significant increase of yield strength.The result of TDA reveals that most of absorbed hydrogen is diffusible hydrogen and the hydrogen content in the tempered specimen is slightly lower than that of the as-forged specimen.The HEI expressed by the relative loss of notch tensile strength before and after hydrogen-charging significantly decreases from 31.8% for the as-forged specimen to 12.8% for the tempered specimen,which is mainly due to the microstructural changes caused by the tempering treatment.