13Cr11Ni2W2MoV马氏体热强不锈钢的韧-脆转变及脆化机理

Ductile-Brittle Transition and Embrittlement Mechanism of 13Cr11Ni2W2MoV Martensitic Heat-resistant Stainless Steel

13Cr11Ni2W2MoV马氏体热强不锈钢用于制备航天火工品构件时,服役温度低至-196℃,需其具有良好的低温冲击韧性。为此本实验研究了13Cr11Ni2W2MoV不锈钢在-150~100℃的夏比冲击性能。采用光学显微镜、扫描电子显微镜和透射电镜分析其显微组织及冲击断口形貌,结合冲击能量及脆性断面率确定了韧-脆转变温度(DBTT),分析了韧-脆转变规律。结果表明:13Cr11Ni2W2MoV不锈钢的DBTT为-35.5℃。温度由100℃降低到-150℃,13Cr11Ni2W2MoV不锈钢的冲击吸收功由180 J降低至30 J。断口放射区主要表现为由撕裂棱和解理面共存的准解理断裂模式,随着温度降低,放射区解理台阶的高度减小,撕裂棱的宽度变窄。纤维区及剪切唇区表现为韧性断裂模式,断口以韧窝为主,随温度降低韧窝的数量及深度减少。裂纹萌生能量及稳定裂纹扩展过程中吸收的能量随温度降低显著下降,裂纹扩展的难度变低,因此发生了韧-脆转变。韧-脆转变的可能原因为低温下位错难以产生和滑动。

13Cr11Ni2W2MoV martensitic heat-strength stainless steel can be used to produce the components of spaceflight igniter,whose working temperature is as low as^(-1)96℃,so it is rather important to investigate the low-temperature impact toughness of the steel.Therefore,Charpy impact properties of 13Cr11Ni2W2MoV steel were measured in the temperature range of-150℃and 100℃.The microstructure and fracture morphology were observed by optical microscope(OM),scanning electron microscope(SEM)and transmission electron microscope(TEM).The ductile-brittle transition temperature(DBTT)was obtained according to the impact energy and the rate of brittle fracture.The results show that the DBTT of 13Cr11Ni2W2MoV is-35.5℃.The impact energy of 13Cr11Ni2W2MoV steel decreases from 180 J to 30 J when the temperature decreases from 100℃to-150℃.The fracture mode of radiation zones is quasi-cleavage,and there are tearing edges and clea-vage facts on the fracture surface.The height of the cleavage steps and the width of the tearing edge are reduced with the decrease of temperature.The fracture mode of fiber zones and shear lip zones is ductile fracture.Dimples are visible on the fracture surfaces.The number and depth of the dimples decrease with the decrease of temperature.The energy for the crack initiation and stable crack propagation are significantly reduced with the decrease of temperature,and the cracks are easy to grow,so the ductile-brittle transition occurs.The ductile-brittle transition might be caused by difficulties of the dislocation generation and slip at low temperatures.