The Effects of Nickel and Carbon Content on the Toughness of an Ultra-High Strength Precipitation Strengthened Stainless Steel

商用和军用飞机起落架通常使用低合金钢300M生产，镀镉以耐腐蚀。在几年内，由于环境问题，镀镉将不可能。 一种可能的替代方案是使用强度水平相当于300 M且不需要镉涂层的不锈钢。这种钢的开发已经引起了飞机制造商、起落架生产商和特种钢公司的极大兴趣。 尽管经过几年的努力，但仍没有开发出具有足够韧性的超高强度不锈钢用于起落架应用。本研究探索了超高强度、沉淀强化马氏体不锈钢的开发，该马氏体不锈钢具有高强度和韧性，并且通过R相颗粒的沉淀来强化。这些钢含有约12wt. %铬、5wt. %钼、12wt. %的钴和至多6wt. %的镍。 这些在钢中的变化预计将导致屈服强度和极限拉伸强度分别为1475MPa和1650MPa，并且还将具有优异的韧性。 该奖项旨在研究钴、钼和碳对这些合金强度和韧性的影响。 为了具有良好的韧性，将主要通过镍含量来控制钢的合金含量，使得钢在淬火状态下含有6至8体积%的残余奥氏体。成功开发用于起落架应用的超高强度不锈钢将满足主要的工业需求。 教育福利包括一名女研究生协助研究的经验。学生将接受培训，使用扫描电子显微镜检查断裂面和X射线衍射测量残余奥氏体含量。学生学习如何使用这些设备和分析方法时，他们正在研究项目，提供这些类型的经验。

Commercial and military aircraft landing gears are often produced using low alloy steel, 300M, with cadmium plating for corrosion resistance. Within a few years, cadmium plating will not be possible because of environmental concerns. A possible alternative is the use of a stainless steel that has strength levels comparable to 300M and does not require cadmium coatings. The development of such a steel has been of great interest to airplane manufacturers, landing gear producers, and speciality steel companies. Despite several years of work, an ultra-high strength stainless steel with sufficient toughness for landing gear applications has not been developed. This research explores the development of an ultra-high strength, precipitation-strengthened martensitic stainless steel that has both high strength and toughness, and is strengthened by the precipitation of particles of R-phase. These steels contain approximately 12 wt. % chromium, 5 wt. % molybdenum, 12 wt. % cobalt, and up to 6 wt. % nickel. Variations of these in the steel are expected to result in yield strength and ultimate tensile strength of 1475MPa and 1650MPa, respectively, and also would have excellent toughness. With this award, the effects of cobalt, molybdenum and carbon are to be examined on the strength and toughness of these alloys. To have good toughness, the alloying content of the steels will be controlled, primarily through the nickel content, so that the steels contain 6 to 8 volume % retained austenite in the as-quenched condition.Successful development of an ultra-high strength stainless steel for landing gear applications will answer a major industrial need. Educational benefits include experience for a female graduate student to assist in the research. Students will be trained to use the scanning electron microscope to examine fracture surfaces and X-ray diffraction to measure retained austenite content. Students learn how to use such equipment and analysis methods when they are working on research projects that provides these types of experiences.