高强镍基耐蚀合金腐蚀行为与σ相关联性及析出控制准则

It is a major concern that remarkable decrease in corrosion resistance is caused by excessive precipitation of sigma phase in high-strength nickel-base alloy components needed urgently in the development of advanced marine vehicle and exploitation of offshore oil and gas in deep water in our country, which has seriously affected the safety of components in the long-term service in the special corrosive environment. However, at present there is a lack of knowledge about the precipitation and evolution mechanism of sigma phase, the corrosion mechanism caused by its precipitation and the quantitative research on relationship between the precipitation amount of sigma phase and corrosion resistance; therefore, so far there is no basis for the improvement of corrosion resistance by controlling the sigma phase precipitation. In the light of the problem, by taking the typical high-strength nickel-base corrosion-resistant alloy as the research object of this research subject, an idea characterized by mechanism and criteria is put forward based on the previous research which investigating the precipitation and evolution mechanism of sigma phase as well as the corrosion mechanism induced by sigma phase in the alloy by combination of experiments, software calculation and numerical analysis. And on this basis, the control criteria of sigma phase precipitation based on corrosion resistance will be established by building the quantitative relationship between the precipitation amount of sigma phase and corrosion resistance combined with the critical precipitation amount of sigma phase causing corrosion damage determined by the corrosion condition and service requirement. This research subject not only can improve the theory about the precipitation and evolution mechanism of sigma phase and the corrosion mechanism caused by the precipitation of sigma phase in high-strength nickel-base corrosion-resistant alloy, but also is expected to accumulate data for the control of corrosion behaviors in advanced structural materials and establish a theoretical basis for reliability of components in service.

目前我国发展先进舰船、深海油气开采等领域急需的高强镍基耐蚀合金构件均存在因σ相过量析出显著降低耐蚀性的问题，已严重影响到长期特种腐蚀条件下构件安全服役。然而，因缺乏对该类合金中σ相析出和演变机制、因其析出导致的腐蚀机制以及σ相析出量与耐蚀性定量关联性的研究，使得目前通过控制σ相析出进而提高合金耐蚀性尚无据可依。针对此问题，申请人以典型高强镍基耐蚀合金为研究对象，在前期研究基础上，基于“两个机制，一个准则”的思路，采用实验、计算和数值分析相结合的方法，研究合金中σ相析出、演变机制以及腐蚀机制，在此基础上，构建σ相析出量与耐蚀性的定量关联性，结合工况腐蚀条件和服役要求确定的临界σ相析出量，建立基于耐蚀性的σ相析出控制准则。本项目不仅可完善高强镍基耐蚀合金中σ相的析出、演变机制及合金腐蚀机制等理论，还可望为实现先进结构材料腐蚀行为可控性积累数据，并为保证构件使役可靠性奠定理论基础。

随着先进舰船装备和深海油气开采等行业的迅速发展，工况环境日益严苛，对其中的镍基合金构件在强度和耐蚀性等方面提出了更高要求。GH4925和GH4945等合金因兼具高强和高耐腐蚀的性能优势，已在相关领域得到了广泛应用。然而，高强镍基耐蚀合金构件存在因σ相过量析出显著降低耐蚀性的问题，已严重影响到长期特种腐蚀条件下构件安全服役。此前，因缺乏对该类合金中σ相析出和演变机制、因其析出导致的腐蚀机制以及σ相析出量与耐蚀性定量关联性的研究，使得通过控制σ相析出进而提高合金耐蚀性尚无据可依。因此，本项目首先通过研究典型高强镍基耐蚀合金时效过程中σ相析出特征及规律，揭示该类合金的σ相析出机制，之后通过研究具有不同σ相析出量的合金腐蚀行为，揭示合金在σ相析出作用下的腐蚀机制，并通过研究典型耐蚀性随σ相析出量的变化关系，建立耐蚀性与σ相析出量的定量关联性表征；最后结合工况腐蚀条件和服役要求，确定导致腐蚀破坏的临界σ相析出量，提出高强镍基耐蚀合金基于耐蚀性的σ相析出控制准则。本项目已公开发表学术论文6篇，其中SCI/EI/收录5篇，获国内发明专利授权2项，申请国内发明专利2项，参加国际和国内重要学术会议并做口头报告各1人次，培养研究生2名。本项目的完成不仅完善了高强镍基耐蚀合金中σ相的析出机制及合金腐蚀机制等理论，还为实现先进结构材料腐蚀行为可控性积累了数据，同时为保证构件使役可靠性及寿命预测奠定了理论基础。