基于氢脆机理的抗氢脆钢表层设计与制备研究

Hydrogen embrittlement has become a major bottleneck that restricting the development of high strength steel. The higher the strength, the higher the susceptibility of hydrogen embrittlement has been accepted by all. With the improvement of smelting and processing levels, the strength of high strength steel is developing in a higher and higher trend, which requires us to develop hydrogen embrittlement-resistant steel. However, to date, comprehensive understanding of hydrogen embrittlement mechanisms is still remain insufficient and the researches on the resistance to hydrogen embrittlement mechanisms are also lacking. To clearly illustrate the mechanisms of hydrogen induced cracking and resistance to hydrogen embrittlement are critical significant to mitigate hydrogen embrittlement and improve the ultimate service properties of materials. In the present application, based on the analysis of fracture morphology induced by hydrogen, firstly, we will clarify the mechanisms of hydrogen induced cracking through the studies of interfaces, microstructure and hydrogen distribution. Secondly, the surface layer with resistance to hydrogen will be designed and prepared based on mechanisms of hydrogen induced cracking and surface modification, the effect of surface modification on the susceptibility of hydrogen embrittlement and the corresponding mechanism of hydrogen induced cracking will be studied, and the inhibitory effect of surface modification on the nucleation and expansion of hydrogen induced cracks will be revealed. At last, the mechanism of resistance to hydrogen embrittlement based on the mechanisms of hydrogen induced cracking and surface modification will be formed. This application will make breakthroughs on hydrogen embrittlement, such as the mechanism of hydrogen induced cracking, the effect of surface modification on hydrogen embrittlement and the inhibitory mechanism of surface modification to the nucleation and expansion of hydrogen induced cracking, it will provide theoretical basis for the design of resistance to hydrogen embrittlement of materials.

氢脆已经成为制约高强度钢发展的主要瓶颈问题。强度越高，氢脆敏感性也越高的规律已经被大家所接受。随着冶炼和加工水平的提高，高强钢的强度朝着越来越高的方向发展，这就更需要我们发展抗氢脆钢。目前关于氢脆机理的认识还不够全面，对抗氢脆机理的研究也偏少。阐明材料的氢致开裂机理与抗氢脆机理对于减缓材料的氢脆，赋予材料极限的服役性能具有重要的意义。本申请以高强钢氢致开裂的断口特征分析为切入点，通过对界面、组织结构与氢分布的研究，揭示高强钢氢致开裂机理；基于氢致开裂机理和表层改性，设计和制备具有阻氢能力的表面层结构，研究表层改性对氢脆敏感性的影响规律以及相应的氢致开裂机理，揭示表层改性对氢致裂纹形核与扩展的抑制作用，形成基于氢脆机理与表层改性的抗氢脆机理。本项目将在高强钢氢致开裂机理、表层改性对氢脆的影响规律以及表层改性抑制氢致裂纹形核与扩展的机理等方面取得突破，为材料的抗氢脆设计提供理论依据。

高强钢的氢脆和断裂问题一直影响着其服役的稳定性和安全性，对于其开裂机理的深入研究有助于减缓氢脆和断裂的产生，从而赋予材料极限的服役性能。本项目从表观现象入手，深入研究了表面变质层的氢脆、演化规律和裂纹扩展机理。项目综合分析了氢浓度对表面变质层划痕深度、宽度、形貌、切向力等参数的影响，计算了高强钢的氢脆性能，研究了氢对材料硬度和断裂韧性的影响，并给出了断裂韧性与氢浓度的经验公式；表征了不同变质层深度的残余应力，给出了残余应力、微观组织和耐蚀性之间的关系；研究了试样表面残余应力在疲劳过程中的演化规律并对其演化机理进行了分析，结果表明，试样表面的残余应力在疲劳过程中均发生了释放，第一个周期的释放最为明显，随着循环次数的增加，残余应力趋于稳定；应力水平会显著影响残余应力释放程度，并存在一个临界值，当施加应力水平小于临界值时，残余应力不发生释放；分析了开裂特征与组织结构的相关性，给出了阻碍裂纹扩展的相关组织特征；研究了裂纹扩展的路径，得到了抑制裂纹扩展的主要因素，揭示了表层改性对裂纹形核与扩展的抑制作用。相关的研究成果为评估高强钢表面变质层的氢脆性能提供了一种可能，对表面变质层的设计和高强钢服役行为的准确评价有着指导性的意义。