时圳演,张言,董立谨,郑淮北,王勤英,刘庭耀.微观组织结构对镍基825合金力学性能和硫化物应力腐蚀开裂的影响[J].表面技术,2023,52(1):141-151.
SHI Zhen-yan,ZHANG Yan,DONG Li-jin,ZHENG Huai-bei,WANG Qin-ying,LIU Ting-yao.NP Effect of Microstructure on Mechanical Properties and Sulfide Stress Corrosion Cracking of Incoloy 825[J].Surface Technology,2023,52(1):141-151
微观组织结构对镍基825合金力学性能和硫化物应力腐蚀开裂的影响
NP Effect of Microstructure on Mechanical Properties and Sulfide Stress Corrosion Cracking of Incoloy 825
  
DOI:10.16490/j.cnki.issn.1001-3660.2023.01.015
中文关键词:  镍基825合金  夹杂物  微观组织结构  三点弯曲实验  硫化物应力腐蚀开裂  慢应变速率拉伸
英文关键词:Incoloy 825  inclusion  microstructure  three-point bending experiment  sulfide stress corrosion cracking  slow strain rate tensile test
基金项目:国家自然科学基金(52001264);海洋装备用金属材料及其应用国家重点实验室开放基金(SKLMEA-K201912)
作者单位
时圳演 西南石油大学 新能源与材料学院,成都 610500 
张言 西南石油大学 新能源与材料学院,成都 610500 
董立谨 西南石油大学 新能源与材料学院,成都 610500 
郑淮北 成都先进金属材料产业技术研究院股份有限公司,成都 610300 
王勤英 西南石油大学 新能源与材料学院,成都 610500 
刘庭耀 成都先进金属材料产业技术研究院股份有限公司,成都 610300 
AuthorInstitution
SHI Zhen-yan School of New Energy and Materials, Southwest Petroleum University, Chengdu 610500, China 
ZHANG Yan School of New Energy and Materials, Southwest Petroleum University, Chengdu 610500, China 
DONG Li-jin School of New Energy and Materials, Southwest Petroleum University, Chengdu 610500, China 
ZHENG Huai-bei Chengdu Advanced Metal Materials Industrial Technology Research Institute Co., Ltd., Chengdu 610300, China 
WANG Qin-ying School of New Energy and Materials, Southwest Petroleum University, Chengdu 610500, China 
LIU Ting-yao Chengdu Advanced Metal Materials Industrial Technology Research Institute Co., Ltd., Chengdu 610300, China 
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中文摘要:
      目的 揭示微观组织结构对镍基825合金硫化物应力腐蚀开裂的影响规律及机理。方法 利用金相显微镜(OM)、扫描电子显微镜(SEM)和背散射电子衍射(EBSD)分析了2种镍基825合金的金相组织、夹杂物种类及等级、晶界类型以及残余应变和晶粒尺寸分布。通过显微维氏硬度计评价了合金的力学性能,同时采用氢微印、动态充氢慢应变速率拉伸试验和三点弯曲试验,评估了合金的氢脆倾向和硫化物应力腐蚀开裂敏感性。结果 2种镍基825合金的夹杂物均以B类和D类TiN为主。2种合金中B类夹杂物均以晶界分布为主,D类夹杂物在合金1#中集中分布,在合金2#中随机分布。合金1#中B类夹杂物等级为0.91,D类夹杂物等级为1.4,合金2#中2种夹杂物等级分别为0.54和1.33。氢微印试验发现氢在合金1#的晶内、晶界处均大面积存在,而在合金2#中则分布稀疏。EBSD发现2种合金均为等轴奥氏体,合金1#晶粒尺寸稍大,晶界以随机大角度晶界为主且存在较高的残余应变集中,而合金2#晶粒细小且尺寸分布更均匀,随机大角度晶界和低Σ界面为其主要晶界类型,残余应变分布均匀。合金1#的硬度为184.67HV,屈服强度为285.30 MPa,而合金2#的硬度和屈服强度分别为207.75HV和300.03 MPa。在动态充氢慢应变速率拉伸试验中,2种合金均出现了氢脆倾向,合金1#的断裂延伸率降低了2.6%,而合金2#只降低了1.6%。三点弯曲试验中合金1#表面发生严重均匀腐蚀,出现了以穿晶为主的宏观裂纹,裂纹萌生部位的基体元素显著降低,在其周围还发现了夹杂物及其脱落留下的微孔,而合金2#表面仍有金属光泽,只有微米级的裂纹萌生于应力集中处。结论 大量夹杂物的存在降低了合金1#的屈服强度并导致晶界残余应变集中,同时作为有效氢陷阱增加了镍基825合金硫化物应力腐蚀开裂的敏感性。此外,夹杂物与金属基体之间形成微电偶,促进周围金属阳极溶解,进一步增加了合金的开裂敏感性。
英文摘要:
      The object of this study is to clarify the effect of microstructure on the sulfide stress corrosion cracking of Incoloy 825. Optical microscope (OM), scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) were used to analyze the metallographic structure, inclusions, grain boundary character, the distribution of residual strain and grain size. The microhardness and mechanical properties of two type of alloy 825 were evaluated by Vickers hardness tester and tensile tests respectively. The susceptibility of hydrogen embrittlement and sulfide stress corrosion cracking were evaluated by hydrogen microprint tests, slow strain rate tensile tests under hydrogen charging, and three-point bending experiments. The results show that the inclusions in these alloys are mainly TiN, which could be divided into type B and D. The distribution of type B inclusions in both alloys are quite similar. Most of inclusions are dispersed near grain boundaries. The distribution of type D inclusions in alloy 1# tends to be concentrated while the inclusions are more homogeneous in alloy 2#. The grades of type B and D inclusions in alloy 1# are 0.91 and 1.4, respectively. However, the quantity and size of inclusions in alloy 2# are smaller, in which the inclusion grades of type B and D are reduced to 0.54 and 1.33, respectively. In addition, MnS and TiN eutectic is formed at a part of grain boundaries of alloy 1#. Hydrogen microprint technique tests confirm that the hydrogen atoms are prone to concentrate at the inclusions and some of grain boundaries in alloy 1#. EBSD analyses show that both of alloys are consisted of equiaxed austenite grains. However, the average grain size of alloy 1# is slightly bigger than that of alloy 2#. In addition, the grain size distribution in alloy 2# is more uniform in comparison to the alloy 1#. The residual strain near the grain boundaries and grain size of alloy 1# is a little higher than that of alloy 2#, in which low Σ boundaries present a large fraction. The microhardness and yield stress of alloy 1# are 184.67HV and 285.30 MPa while the alloy 2# has a microhardness of 207.75HV and a yield stress of 300.03 MPa. The result of slow strain rate tensile tests under hydrogen charging revealed a tendency of hydrogen embrittlement for both alloys. The fracture elongation of alloy 1# decreased by 2.6% while that of alloy 2# only decreased by 1.6%. The difference of mechanical properties may be attribute to the distribution of inclusions and grain size. Three-point bending experiments indicate the surface of alloy 1# is severely corroded, and macroscopic cracks are found near the opening. High-magnification observation of the crack initiation region reveal that inclusions and cavities existed at the crack site in alloy 1#. After initiation, the cracks propagate mainly transgranularly. Nevertheless, the surface of alloy 2# still shows the metallic luster and only small cracks with a size of several microns exist at the stress concentration region. In conclusion, the inclusions as effective hydrogen traps, reduce the yield stress and lead to residual strain concentration at grain boundaries, thus result in the sulfide stress corrosion cracking of alloy 825. In addition, a galvanic cell could form between the inclusion and surrounding metal, promotes the anodic dissolution of the matrix, and therefore the cracking susceptibility of the alloy is increased.
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