Gas-Phase Nitridation under Kinetic Control -- A New Concept for Surface Hardening of Ti-Base Alloys

动力学控制下的气相氮化——钛基合金表面硬化的新概念

• 批准号: 0506711
• 负责人: Frank Ernst
• 金额: --
• 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: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0506711&HistoricalAwards=false
• 关键词: Gas; Phase; Nitridation; under; Kinetic

Technical: Ti-base alloys are technologically important because of their high specific strength and resistance against corrosion in oxidizing environments. However, in many applications (aerospace engineering, biomedicine, sports, jewelry, architecture) the performance of such alloys is severely limited by their notoriously poor surface hardness and scratch resistance, very high friction coefficients and rapid wear, as well as poor corrosion resistance in reducing media. A powerful approach to counter these deficiencies is to harden the surface of Ti-alloy parts preferentially after they have been formed into their final shape. Such "case" hardening is most effectively achieved by Inward diffusion of interstitial solutes, for example nitrogen. However, titanium forms very stable compounds with all relevant interstitial solutes. Consequently, conventional methods to case-harden Ti-base alloys with interstitial solutes inevitably produce precipitates (oxides, carbides, or nitrides), which severely degrade the wear-, fatigue-, and corrosion resistance. Pioneering experiments by the PI's group have resulted in a new concept enabling inward diffusion of nitrogen into titanium base alloys from a gas phase without precipitating detrimental nitride particles. This new concept is denoted as "Nitridation under kinetic control" and has been successfully implemented in two different processing schemes, yielding precipitation-free cases with nitrogen concentrations of up to 20 at% and a tremendous increase in surface hardness. In this investigation, the PIs propose to study the surface, microstructure, and fundamental properties of these new and unusual materials. Non-Technical: The broader impacts of this work include new engineering applications of parts and components made from Ti-base alloys, new jobs related to these new applications, savings of primary energy related to the high specific strength of Ti-base alloys in some of these new applications, advances in fighting diseases by making available better materials for medicalimplants, and improvements in aircraft safety - e. g. by reducing catastrophic failureof Ti-base alloy hydraulic lines in helicopters. The results of the proposed project will also profoundly impact materials science courses at CWRU. Both PIs have a record of supporting underrepresented minorities and have had a substantial fraction of women students in their research groups. The Co-PI has a continuing effort of introducing middle school students to materials science and microscopy.

技术：钛基合金在技术上很重要，因为它们具有高比强度和抗氧化环境腐蚀的能力。然而，在许多应用中（航空航天工程、生物医学、体育、珠宝、建筑），这些合金的性能受到其众所周知的低表面硬度和抗刮擦性、非常高的摩擦系数和快速磨损以及在还原介质中的耐腐蚀性差的严重限制。克服这些缺陷的一种有效方法是在钛合金零件成形后优先对其表面进行硬化。这种“外壳”硬化最有效的实现方式是向内扩散的间隙溶质，例如氮。然而，钛与所有相关的间隙溶质形成非常稳定的化合物。因此，使用间隙溶质对ti基合金进行表面硬化的传统方法不可避免地会产生析出物（氧化物、碳化物或氮化物），从而严重降低其耐磨性、抗疲劳性和耐腐蚀性。PI小组的开创性实验产生了一种新概念，使氮气从气相向内扩散到钛基合金中，而不会析出有害的氮化物颗粒。这个新概念被称为“动力学控制下的氮化”，并已成功地在两种不同的处理方案中实施，产生了无沉淀的情况，氮浓度高达20%，表面硬度大大提高。在这项研究中，pi建议研究这些新的和不寻常的材料的表面，微观结构和基本性质。非技术:这项工作的广泛影响包括由钛基合金制成的零部件的新工程应用，与这些新应用相关的新工作，在某些新应用中与钛基合金的高比强度相关的一次能源节约，通过提供更好的医疗植入材料来对抗疾病的进步，以及提高飞机安全性-例如通过减少直升机上钛基合金液压管线的灾难性故障。该项目的研究结果也将对CWRU的材料科学课程产生深远的影响。两位pi都有支持代表性不足的少数民族的记录，并且在他们的研究小组中有相当一部分女性学生。Co-PI一直致力于向中学生介绍材料科学和显微镜。