GH3128合金在950 ℃静态长期时效过程中组织演变研究

Study on Microstructure Evolution of GH3128 Alloy During Long-Term and Static Aging at 950 ℃

摘要:

GH3128合金为固溶强化型镍基高温合金，在高温下具有强度高、塑性好、抗氧化性能优异及焊接、加工性能良好等优点，可作为长期在950 ℃下服役的零部件的材料。为研究GH3128合金在950 ℃及不同气氛（空气和氦气）下微观组织演变规律及力学性能稳定性，分别进行了100、300、500、1 000和3 000 h的长效试验。利用SEM、电解萃取+X射线衍射分析等方法，对时效后合金中析出相和析出相中主要元素含量进行了表征和定量分析。同时，通过室温及高温拉伸测试评估合金长时效后的力学性能的稳定性，以及合金组织演变对性能稳定性的影响。结果表明，锻造态GH3128合金中主要析出相为M(Mo、W、Ni)₆C，在950 ℃、空气和氦气两种气氛下长时效过程中合金组织演变规律基本保持一致，随时效时间的延长合金中碳化物含量呈现先增加后平缓的趋势，且晶界上碳化物逐渐粗化并呈连续性分布。在空气和氦气两种气氛下长时效过程中合金均析出有害相（μ相），且随着时效时间延长，μ相由短棒状转变为针状，其含量呈现先增加后平缓的趋势。与空气气氛相比较，在氦气气氛下时效析出的碳化物和μ相含量较低。GH3128合金在两种气氛下时效不同时间后，室温及高温拉伸强度基本保持稳定，拉伸塑性总体呈现先下降后平稳的趋势，时效1 000 h后基本达到稳定状态。结合GH3128合金时效过程中组织演变规律，进一步证明时效过程中μ相、M(Mo、W、Ni)₆C相含量的增加及形貌的转变均对合金塑性产生不利影响。对GH3128合金在不同气氛下时效后的组织和性能演变规律进行表征分析，为扩大其应用提供一定的理论依据。(专精特新·特殊环境材料服役行为专辑十五之七)

Abstract:

The microstructure evolution and the stability of mechanical properties of GH3128 alloy under different atmospheres at 950 ℃ were investigated in this paper. Long-term aging tests were carried out at 950 ℃ for 100， 300， 500， 1 000 and 3 000 h at 950 ℃， respectively， in air and helium atmospheres. The precipitated phases and main element in the precipitated phase after aging were characterized and quantitatively analyzed by SEM， electrolytic extraction and X-ray diffraction analysis. The stability of mechanical properties of the alloy after long-term aging was evaluated by tensile tests at room temperature and high temperature， and the influence of microstructure evolution on the property stability was determined. The results reveal that the main precipitated phase in the wrought GH3128 alloy is M（Mo，W，Ni）₆C. During the long-term aging process at 950 ℃ in air and helium atmospheres， the microstructure evolution of GH3128 alloy is essentially consistent. With the increase of aging time， the carbides content in the alloy demonstrates a trend of initially increasing and then flattening. Carbides gradually coarsen along the grain boundary， presenting a continuous distribution. During the long-term aging process in both air and helium atmospheres， the harmful μ-phases precipitate out in the alloy， and with the extension of aging time， the μ-phases transform from short rod to needle， and the content increase initially and then flatten. Compared with the air atmosphere， the contents of carbides and μ phases precipitated during the aging process in the helium atmosphere are lower. The tensile strength of GH3128 alloy remains relatively stable at room temperature and high temperature after aging for different durations in the two atmospheres， and the tensile plasticity exhibits a trend of initially decreasing and then stabilizing， and basically reaches a stable state after aging for 1 000 h. Combined with the microstructure evolution of GH3128 alloy during aging， it can be further demonstrated that the increase in μ-phases， M（Mo， W， Ni）₆C content and the change of morphology during aging have adverse effects on the plasticity of the alloy.