Paraequilibrium Carbides in Stainless Steels

不锈钢中的准平衡碳化物

• 批准号: 1104937
• 负责人: Arthur Heuer
• 金额: $ 45万
• 依托单位: Case Western Reserve University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1104937&HistoricalAwards=false
• 关键词: Paraequilibrium; Carbides; Stainless; Steels

TECHNICAL SUMMARY: Ferritic, martensitic, and duplex stainless steels, optimally carburized at temperatures below 500 °C, possess a hardened case containing a remarkable class of carbide phases that do not degrade, and in certain cases actually improve the corrosion resistance of these important steels. Analyses of these carbides have determined that they have the same metal compositions as those of the bulk stainless steels in which they formed, and thus are termed paraequilibrium carbides. Inasmuch as the formation of these paraequilibrium carbides do not deplete the surrounding matrix of Cr, "sensitization" and loss of corrosion resistance does not occur. The proposed research will fully characterize the structure, microstructure, and stoichiometry of these paraequilibrium carbides, and their effect on electro-chemical, tribological, and mechanical properties of the interstitially hardened steel surfaces. A range of processing parameters, e.g., time/temperature and carbon activity in the process gas atmosphere, will be applied to these stainless steels to generate a broad spectrum of paraequilibrium carbide phases. Thermodynamic and kinetic modeling will be performed in parallel with the processing and characterization activities to provide in-depth understanding of this exciting technology.NON-TECHNICAL SUMMARY: Low-temperature carburization of austenitic (high nickel content) stainless steels is now employed on an industrial scale in a number of important applications. Similar technology is not now generally available for ferritic, martensitic, and duplex stainless steels. Successful low-temperature carburization of this important group of magnetic stainless steels---which furthermore are less costly due to their greatly reduced nickel content---will have broad impact. A properly hardened carburized surface will enable these stainless steels to establish new applications and new markets, based upon improved wear and corrosion resistance, in addition to their other useful properties. Finally, the student researchers doing their thesis research on this topic will experience a rich array of activities involving processing, characterization and modeling, all against the backdrop of a constrained optimization project.

技术概要：铁素体、马氏体和双相不锈钢最好在低于500 °C的温度下渗碳，具有硬化的表面，其中含有一类不降解的碳化物相，在某些情况下实际上提高了这些重要钢的耐腐蚀性。对这些碳化物的分析已经确定，它们具有与它们形成的大块不锈钢相同的金属组成，因此被称为准平衡碳化物。由于这些准平衡碳化物的形成不会耗尽周围基质中的Cr，因此不会发生“敏化”和耐腐蚀性损失。拟议的研究将充分表征这些准平衡碳化物的结构，微观结构和化学计量，以及它们对电化学，摩擦学和机械性能的影响，淬火钢表面。处理参数的范围，例如，时间/温度和工艺气体气氛中的碳活性将应用于这些不锈钢以产生宽谱的准平衡碳化物相。热力学和动力学建模将与加工和表征活动并行进行，以深入了解这种令人兴奋的技术。非技术总结：奥氏体（高镍含量）不锈钢的低温渗碳现在在许多重要应用中以工业规模使用。类似的技术目前还不能普遍用于铁素体、马氏体和双相不锈钢。这一重要磁性不锈钢组的成功低温渗碳-由于其镍含量大大降低，成本更低-将产生广泛的影响。适当硬化的渗碳表面将使这些不锈钢能够建立新的应用和新市场，除了它们的其他有用特性之外，还基于改进的耐磨性和耐腐蚀性。最后，学生研究人员做他们的论文研究这一主题将经历一系列丰富的活动，涉及处理，表征和建模，所有的约束优化项目的背景下。