Fedorov Aleksandr, Karasev Vladimir, Kovalev Pavel, Shaposhnikov Nikita, Zhitenev Andrey
Scientific and Technical Complex «New Technologies and Materials», Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia.
Institute of Machinery, Materials, and Transport, Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia.
Materials (Basel). 2024 Jan 7;17(2):294. doi: 10.3390/ma17020294.
One of the most popular methods for ranking duplex stainless steels (DSSs) and predicting their corrosion properties is the calculation of the pitting resistance equivalent number (PREN). However, since DSSs are two-phase materials with a significant fraction of secondary phases and precipitates, the application of the PREN can be highly limited. This article attempted to use a new approach to describe the corrosion resistance of these steels. The corrosion resistance of two DSSs of the same class was investigated. Under identical solution heat treatments in the temperature range of 1050-1200 °C, the crevice corrosion resistance of one steel increased, while that of the other decreased. It was demonstrated that the amounts of austenite and ferrite changed similarly in these steels, and the different corrosion resistances were associated with the behaviors of secondary phases: niobium carbonitride and chromium nitride. SEM-EDS analysis was conducted to analyze the redistribution of elements between phases in both cases, showing good agreement with the thermodynamic modeling results. The PREN was calculated for each phase depending on the treatment temperature, and a method for calculating the effective PREN (), accounting for phase balance and secondary phases, was proposed. It was shown that this indicator described corrosion properties better than the classical PREN calculated for the average steel composition. This study demonstrated how the calculation of critical temperatures (the temperature of equal amounts of ferrite and austenite, the temperature of the beginning of chromium nitride formation, and the temperature of the beginning of σ-phase formation) could describe the corrosion resistance of DSSs. Maximum possible deviations from these temperatures were defined, allowing the attainment of the required corrosion properties for the steels. Based on the conducted research, an approach for selecting new compositions of DSSs was proposed.
对双相不锈钢（DSS）进行排名并预测其腐蚀性能最常用的方法之一是计算耐点蚀当量数（PREN）。然而，由于DSS是具有大量第二相和析出物的两相材料，PREN的应用可能会受到很大限制。本文尝试采用一种新方法来描述这些钢的耐腐蚀性。研究了同一类别的两种DSS的耐腐蚀性。在1050 - 1200℃温度范围内进行相同的固溶热处理时，一种钢的耐缝隙腐蚀性增加，而另一种钢的耐缝隙腐蚀性降低。结果表明，这些钢中奥氏体和铁素体的含量变化相似，不同的耐腐蚀性与第二相（碳氮化铌和氮化铬）的行为有关。进行了扫描电子显微镜 - 能谱分析（SEM - EDS）以分析两种情况下相之间元素的重新分布，结果与热力学建模结果吻合良好。根据处理温度计算了每个相的PREN，并提出了一种考虑相平衡和第二相的有效PREN（）的计算方法。结果表明，该指标比根据平均钢成分计算的经典PREN能更好地描述腐蚀性能。本研究展示了如何通过计算临界温度（铁素体和奥氏体等量时的温度、氮化铬形成开始时的温度以及σ相形成开始时的温度）来描述DSS的耐腐蚀性。确定了与这些温度的最大可能偏差，从而使钢能够达到所需的腐蚀性能。基于所进行的研究，提出了一种选择新型DSS成分的方法。
