Plasma Nitriding Properties of Sintered Body Formed Using CoCrFeMnNi High-Entropy Alloy Powder by Varying Ball-Milling Duration
Plasma Nitriding Properties of Sintered Body Formed Using CoCrFeMnNi High-Entropy Alloy Powder by Varying Ball-Milling Duration
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DOI：
10.1007/s00501-023-01326-7
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发表时间：
2023-03
期刊：
影响因子：
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通讯作者：
Jiaxin Peng;A. Nishimoto
中科院分区：
文献类型：
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作者：
Jiaxin Peng;A. Nishimoto
最近，CoCrFeMnNi高熵合金（HEA）被报道在低温下具有优异的拉伸强度和延展性。通过在673 K下的等离子体渗氮，在该HEA表面上形成了膨胀的面心立方结构。另一项研究发现，在球磨时，在CoCrFeMn合金粉末的表面上引入位错，因此同时发生强度提高和应变硬化。本研究的目的是评估的特性的氮化层通过直流等离子体氮化（DCPN）处理的烧结体的钴铬铁锰镍HEA粉末球磨后形成的。具体地，对气体雾化的CoCrFeMnNi HEA粉末样品进行第一次球磨，持续时间范围为0至15小时，以制备烧结体。接着，在75%N2 - 25%H2、200 Pa的气压下，在673 K下对各烧结体进行15小时的DCPN处理。在离子渗氮过程中，安装了奥氏体不锈钢屏作为辅助阴极，以确保均匀加热和高氮供应。此外，通过X射线衍射（XRD）、横截面显微组织观察、表面形貌观察、维氏硬度测试、辉光放电光学发射光谱分析（GD-OES）、腐蚀测试和磨损测试对每个氮化样品进行了表征。XRD和GD-OES测试结果表明，随着球磨时间的延长，样品表面的N浓度逐渐降低。维氏硬度测试结果表明，随着球磨时间的延长，合金表面硬度逐渐增加。电子探针和扫描电子显微镜分析结果表明，沉积层和氮化层分离的所有等离子体渗氮样品的表面上。磨损试验表明，随着球磨时间的增加，磨痕的宽度和深度减小，从而样品呈现出增加的耐磨性。
Recently, a CoCrFeMnNi high-entropy alloy (HEA) was reported to possess excellent tensile strength and ductility at low temperatures. By plasma nitriding at 673 K, an expanded face-centered cubic structure was formed on the surface of this HEA. Another study found that, on ball milling, dislocations were introduced on the surface of a CoCrFeMn alloy powder and consequently strength improvement and strain hardening occured simultaneously. The present study aimed to evaluate the characteristics of the nitrided layer obtained by direct-current plasma nitriding (DCPN) treatment of the sintered body of a CoCrFeMnNi HEA powder formed after ball milling. Specifically, first ball-milling was conducted on gas-atomized CoCrFeMnNi HEA powder samples for durations ranging from 0 to 15 h to prepare sintered bodies. Subsequently, each sintered body was subjected to DCPN treatment at 673 K for 15 h at a gas pressure of 200 Pa under 75% N2−25% H2. During the plasma nitriding process, an austenitic stainless-steel screen was installed as an auxiliary cathode to ensure uniform heating and high nitrogen supply. Furthermore, each nitrided sample was characterized by X‑ray diffraction (XRD), cross-sectional microstructure observations, surface morphology observations, Vickers hardness tests, glow discharge optical emission spectroscopic analysis (GD-OES), corrosion tests, and wear tests. The XRD and GD-OES results showed that N concentration on the surface decreased with the ball milling duration. Based on the Vickers hardness tests, the surface hardness increased with the ball milling duration. Electron-probe microanalysis and scanning electron microscopy results exhibited that the deposited and nitrided layers separated on the surfaces of all plasma-nitrided samples. The wear tests showed that the widths and depths of the wear marks decreased with increasing ball milling duration, and thus the samples presented an increased wear resistance.