Abstract

Vacuum carburizing with high-pressure gas quenching is increasingly employed to reduce near-surface intergranular oxidation and reduce quenching distortion. Vacuum carburizing can be conducted at higher operating temperatures, as high as 1100 °C, to reduce the processing times and increase furnace productivity. However, processing at elevated temperatures may result in excessive austenite grain coarsening, leading to the degradation of fatigue performance. Microalloying to form small carbo-nitride precipitates is one effective method to limit austenite grain growth during carburizing. In this study, the effects of microalloying a carburizing steel with molybdenum (Mo) and niobium (Nb) on microstructural grain refinement in the core have been investigated. Additions of Nb alone are found to provide some control of abnormal austenite grain growth. Additions of Mo in combination with Nb provide enhanced resistance to austenite grain growth, especially at high carburizing temperatures up to 1050 °C. The enhanced control is attributed to solute and precipitation effects.

中文翻译：

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Mo与Nb结合对真空渗碳钢奥氏体晶粒尺寸控制的影响

摘要

越来越多地采用带有高压气体淬火的真空渗碳方法来减少近表面的晶界氧化并减少淬火变形。真空渗碳可在更高的工作温度（高达1100°C）下进行，以减少加工时间并提高炉子生产率。但是，在高温下加工可能会导致奥氏体晶粒过度粗化，从而导致疲劳性能下降。微合金化形成小的碳氮化物沉淀是限制渗碳过程中奥氏体晶粒长大的一种有效方法。在这项研究中，研究了用钼（Mo）和铌（Nb）对渗碳钢进行微合金化对芯部组织细化的影响。发现单独添加Nb可以控制异常奥氏体晶粒的生长。Mo与Nb的结合可增强对奥氏体晶粒长大的抵抗力，尤其是在高达1050°C的高渗碳温度下。增强的控制归因于溶质和沉淀效应。