Ultrahigh Current Density Nitrogen Ion Implantation-- Effects on the Microstructure and High Cycle Fatigue Properties

最有前途的现代表面改性工艺之一是 离子注入 为了实现低成本的离子注入， 独特的宽光束（直径10 cm）超高电流密度（高达1500 微A/平方厘米与传统的6微A/平方厘米离子相比 科罗拉多州立大学开发了该系统。 的 主要研究者将研究高电流密度的影响 离子注入 在高电流下达到高温 密度，但短的注入时间没有产生任何变化， 块体（植入区下方）硬度或块体显微结构 1018马氏体钢和许多其他合金在高电流下 密度离子注入 PI将调查以下内容 高电流密度离子注入的各个方面： 基于时间和温度的钢的电流密度 B）钢的硬度和合金含量的比较， 氮离子注入α-铁形成的氮化物相 通过电子金相法测定的低和高电流密度，以及c） α-铁的高周疲劳抗力的比较 传统的低电流密度（10微安/平方厘米）和CSU 高电流密度（1500微安/平方厘米）氮离子 置入 PI观察到， 氮离子在高电流密度，导致更大的 表面滑移的阻滞。 阻滑可以延缓开裂 在高周疲劳中引发并增加疲劳寿命。

One of the most promising modern processes for surface modification is ion implantation. In order to achieve low cost ion implantation, a unique broad beam (10 cm.dia.) ultrahigh current density (up to 1500 Micro A/Square cm compared to conventional 6 Micro A/Square cm) ion implanter has been developed at the Colorado State University. The Principal Investigator will study the effects of high current density ion implantation. High temperatures are reached at high current densities, but the short implantation time produced no change in the bulk (beneath implanted zone) hardness or bulk microstructure in blocks of 1018 martensitic steel and many other alloys following high current density ion implantation. The PI will investigate the following aspects of high current density ion implantation: a) Permissible current densities for steels based on the time and temperature of implantation and the alloy content of steels, b) Comparison of the hard nitride phases formed due to nitrogen ion implantation in alpha-iron at low and high current densities by electron metallography, and c) Comparison of high cycle fatigue resistance of alpha-iron subjected to conventional low current density (10 Micro A/Square cm) and the CSU high current density (1500 Micro A/Square cm) nitrogen ion implantation. The PI has observed a four fold increase in the range of nitrogen ions at high current densities, resulting in a greater retardation of surface slip. Slip retardation would delay crack initiation in high cycle fatigue and increase fatigue life.