Formation and Properties of Nitrocarburizing S-Phase on AISI 316L Stainless Steel-Based WC Composite Layers by Low-Temperature Plasma Nitriding
Formation and Properties of Nitrocarburizing S-Phase on AISI 316L Stainless Steel-Based WC Composite Layers by Low-Temperature Plasma Nitriding
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DOI：
10.3390/met11101538
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发表时间：
2021-09
期刊：
影响因子：
2.9
通讯作者：
S. Adachi;T. Yamaguchi;N. Ueda
中科院分区：
文献类型：
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作者：
S. Adachi;T. Yamaguchi;N. Ueda
采用激光熔覆技术制造的不锈钢基WC复合层，具有很强的机械强度。然而，WC复合层的耐磨性不足以在剧烈摩擦磨损环境下使用，并且由于二次碳化物的形成而使耐腐蚀性显着降低。奥氏体不锈钢的低温等离子渗氮和渗碳，在低于450℃的温度下处理，可以产生氮或碳的过饱和固溶体，称为S相。渗氮和渗碳联合处理可形成氮碳共渗S相，其特点是层厚、截面硬度分布优越。在激光熔覆过程中，WC颗粒分解产生游离碳。为了获得优异的耐磨性和耐腐蚀性，我们尝试仅通过等离子渗氮，使用这种游离碳在 AISI 316 L 不锈钢基 WC 复合层上形成氮碳共渗 S 相。结果，形成厚的氮碳共渗S相。 S相的维氏硬度范围为1200~1400HV，硬度深度分布变得更加平滑。由于溶解在 AISI 316 L 钢基体中的氮，提高了耐点蚀当量数，从而提高了耐腐蚀性。
Stainless steel-based WC composite layers fabricated by a laser cladding technique, have strong mechanical strength. However, the wear resistance of WC composite layers is not sufficient for use in severe friction and wear environments, and the corrosion resistance is significantly reduced by the formation of secondary carbides. Low-temperature plasma nitriding and carburizing of austenitic stainless steels, treated at temperatures of less than 450 °C, can produce a supersaturated solid solution of nitrogen or carbon, known as the S-phase. The combined treatment of nitriding and carburizing can form a nitrocarburizing S-phase, which is characterized by a thick layer and superior cross-sectional hardness distribution. During the laser cladding process, free carbon was produced by the decomposition of WC particles. To achieve excellent wear and corrosion resistance, we attempted to use this free carbon to form a nitrocarburizing S-phase on AISI 316 L stainless steel-based WC composite layers by plasma nitriding alone. As a result, the thick nitrocarburizing S-phase was formed. The Vickers hardness of the S-phase ranged from 1200 to 1400 HV, and the hardness depth distribution became smoother. The corrosion resistance was also improved through increasing the pitting resistance equivalent numbers due to the nitrogen that dissolved in the AISI 316 L steel matrix.