摘要
沉淀强化Fe-Ni基奥氏体合金具有高强度、优异的耐腐蚀性和较低的氢脆敏感性,因而被广泛应用于航空航天、氢能源工程和石油化工等领域。相对于现有铸锻造等技术,增材制造工艺能够实现复杂形状零件近净成形。采用激光熔化沉积制备NASA-HR(NHR)抗氢钢,研究高温固溶(930~1180℃)、时效处理(725~775℃)热处理工艺条件对其微观结构演变、力学性能和抗氢性能的影响。结果表明,由于激光熔化沉积过程中温度梯度高和熔凝速度快,其凝固组织主要由柱状晶组成,并在枝晶区域出现Ti元素偏析。经1180℃高温固溶处理后,激光熔化沉积NHR合金熔池特征消失,成功消除Ti元素偏析并获得完全再结晶均匀组织。随后分别经过725、750和775℃时效处理,发现随着时效温度升高,晶粒尺寸略微生长,γ′相纳米析出尺寸逐渐变大,产生的析出强化效应越大,合金强度明显升高。在775℃时效处理后强度达到1070 MPa,塑性略有降低,但其断后伸长率均保持在26%以上,拉伸断口形貌均由韧窝组成呈韧性断裂。优化热处理条件下可以使得增材制造NHR合金在力学性能上与锻态匹配。锻造和增材制造NHR合金氢致塑性损减分别是21.7%和20.8%,氢脆敏感性相当。充氢后两者拉伸断口均出现沿晶断裂特征,为韧脆混合断裂。增材制造NHR合金在力学性能和抗氢性能上的良好匹配,为增材制造抗氢钢在临氢环境下的服役性能提供参考,并为增材制造抗氢钢的应用开拓思路。
Precipitation-strengthened Fe-Ni based austenitic alloys possess high strength,excellent corrosion resistance,and low hydrogen embrittlement sensitivity,thus being widely used in sectors such as aerospace,hydrogen energy engineering,and petrochemicals.In comparison to existing casting and forging techniques,additive manufacturing can achieve near-net shaping of intricately shaped components.NASA-HR(NHR)hydrogen-resistant steel was fabricated by laser melting deposition,and the effects of heat treatment process conditions,including hightemperature solid solution(930-1180℃)and aging treatment(725-775℃),on its microstructural evolution,mechanical properties,and hydrogen-resistant properties are studied.The results indicate that due to the high tem‐perature gradient and rapid melting rate during the laser melting deposition process,the solidification structure is primarily composed of columnar crystals,with Ti element segregation observed in the dendrite region.After solid solution treatment at 1180℃,the characteristic features of the NHR alloy melt pool during laser melting deposition dissipated,effectively eliminating Ti element segregation and achieving a uniformly recrystallized structure.Subsequent aging treatments at 725℃,750℃,and 775℃revealed that as the aging temperature rose,grain size slightly increased,with the size ofγ′phase nano-precipitates gradually widening,leading to an enhanced precipitation strengthening effect and a significant rise in alloy strength.After aging at 775℃,the strength reached 1070 MPa,with a slight reduction in plasticity;however,its elongation after fracture consistently exceeded 26%,and the tensile fracture morphology was characterized by ductile dimples,exhibiting ductile fracture characteristics.Optimizing heat treatment conditions can align the mechanical properties of NHR alloys produced via additive manufacturing with those of the forged state.The reduction in hydrogen-induced plastic damage for the NHR alloy in forging and additive manufacturing is 21.7%an
作者
张子雨
李佶纳
刘赓
苏杰
王敖
ZHANG Ziyu;LI Jina;LIU Geng;SU Jie;WANG Ao(Institute of Special Steels,Central Iron and Steel Research Institute,Co.,Ltd.,Beijing 100081,China;Technology Center,Anshan Steel Co.,Ltd.,Anshan 114009,Liaoning,China)
出处
《钢铁》
CAS
CSCD
北大核心
2024年第6期94-103,共10页
Iron and Steel
基金
国家自然科学基金资助项目(52101131)。
关键词
激光熔化沉积
NASA-HR合金
偏析
力学性能
氢脆敏感性
laser melting deposition
NHR alloys
segregation
mechanical property
hydrogen embrittlement susceptibility
