奥氏体不锈钢低温超饱和渗碳表面强化及抗疲劳和腐蚀性能的研究

Carburization at low temperature colossal supersaturation is a novel surface hardening method, which can not only enhance surface hardeness and wear resistance of austenitic stainless steels, and but also enhance their fatigue and corrosion resistance. This has the important application prospects in the industrial fields such as chemical, petrochemical, energy and so on. In this project, the effect of multi-factors including the gas component ratio, temperature and time on surface hardening will be studied for 316L and 304 austenitic stainless steels, and the surface hardening technique based on low temperature colossal carbon supersaturation will be optimized. Interaction between carbon and main metal elements in the matrix will be anlyazed for carburization at low temperature colossal supersaturation, the carburized layer growth will be studied by predicting the carbon diffusion at the different treatment conditions. The surface hardening mechanism of austnitic stainless steel caburized by low temperature colossal carbon supersaturation will be revealed. The prediction method of carbon diffsuion induced residual stress in carburization at low temperature colossal supersaturation will be developed. Combined with residual stress measurement, the compressive residual stress value and its distribution produced in the surface hardening will be correctly obtained. The fatigue and corrosion resistance of austenitic stainless steels carburized through low temperature colossal supersaturation will be comprehensively evaluated by analyzing the internal relationship between surface hardeness, microscopic phases, compressive residual stress and fatigue and corrosion behavior.The research results can give the scientific guidance on industrial application of surface hardening by carburization at low temperature colossal supersaturation.

低温超饱和渗碳是一种新的表面强化方法，不仅能提高奥氏体不锈钢表面硬度和抗磨损性能，而且也能提高抗疲劳和腐蚀开裂性能，在化工、石油化工、能源等工业领域具有重要的应用前景。本项目以工业中广泛应用的316L和304奥氏体不锈钢为研究对象，借助理论分析、数值模拟和试验测试等方法，研究多因素（气氛比例、温度和时间）对低温超饱和渗碳表面强化效果的影响，优化表面强化处理工艺；研究碳和基体主要成分之间的交互作用，预测不同强化处理条件下碳扩散，研究渗碳层生长规律，揭示奥氏体不锈钢低温超饱和渗碳表面强化的机理；发展低温超饱和渗碳时碳扩散诱发的残余应力预测方法，结合残余应力的测量，准确预测表面强化处理形成的压缩残余应力大小和分布规律；分析表面硬度、微观相和压缩残余应力与疲劳和腐蚀间的内在联系，综合评价表面强化的奥氏体不锈钢抗疲劳和腐蚀性能。研究成果为低温超饱和渗碳表面强化处理的工业化应用提供科学指导。

低温超饱和气体渗碳（也称低温气体渗碳）是一个新的表面强化方法，不仅能提高奥氏体不锈钢表面硬度和抗磨损性能，而且也能提高其抗疲劳和腐蚀开裂性能，在核电、石油化工、海洋船舶、能源等行业领域等工业领域具有重要的应用前景。 本项目以工业中广泛应用的316L和304奥氏体不锈钢为研究对象，对低温气体渗碳表面强化特征、机理及其影响因素进行了深入研究。研究了多因素（气体组分比例、温度和时间）对低温气体渗碳表面强化的影响，获得了最佳的表面强化处理工艺。在优化的低温气体渗碳工艺条件下，研究了表面形貌对强化效果的影响，确定了适合进行渗碳强化的表面形貌。研究了碳和基体主要成分之间的交互作用，预测了不同强化处理条件下碳在材料中的扩散和溶解。通过扩散理论和弹塑性本构方程的建立，并综合考虑与碳浓度相关的力学性能参数，发展了扩张奥氏体中残余应力的预测方法。分析了渗碳层中所形成的相及其与表面硬度的内在关系，揭示了奥氏体不锈钢低温气体渗碳表面强化机理。研究了表面硬度、微观相和压缩残余应力与疲劳和腐蚀开裂的内在联系。研究表明低温气体渗碳表面强化的奥氏体不锈钢抗疲劳强度提高20%以上，而抗腐蚀开裂时间提高4倍以上，显著提高了奥氏体不锈钢抗疲劳和抗腐蚀性能。研究成果对低温气体渗碳表面强化方法的推广应用提供科学指导。