AISI 1005 Steel Plasma Treated by Different Thermochemical Surface Treatments

Abstract To modify the surface structure of AISI 1005 steel and its properties without any dimensional loss, different plasma surface treatments were performed at low temperatures (500 ºC) in this study. The samples were subjected to single plasma treatments including: nitriding (N5% and N3%), carburizing (CE) and ferritic nitrocarburizing (NC) and to duplex treatments of nitriding followed by carburizing (N5%+CE and N3%+CE) and ferritic nitrocarburizing followed by carburizing (NC+CE). The gas mixture used for these treatments was varied as follows: nitriding (5%N2+95%H2 and 3%N2+97%H2), carburizing (5%CH4+95%H2) and ferritic nitrocarburizing (5%N2+1.5%CH4+93.5%H2). A microstructural characterization of the samples was carried out using optical and scanning electron microscopy in addition to XRD analysis. Microhardness testing was also performed. The XRD analysis showed a stabilization of the outermost cementite layer for all of the carburizing treatments. The results show that a greater hardness increase was achieved for the nitriding treatment as well as a more regular compound layer. However, a greater depth of hardening was obtained in samples with NC+CE and N5%+CE, which extended to the hardened depth to 800 µm.

摘要：为在无尺寸损耗的前提下改性AISI 1005钢的表面结构与性能，本研究于低温（500 ℃）条件下开展了不同等离子表面处理（plasma surface treatment）实验。实验试样分别接受单一等离子表面处理与复合等离子表面处理：单一处理包括氮化（Nitriding，分为N5%与N3%两组）、渗碳（Carburizing，简称CE）以及铁素体氮碳共渗（Ferritic Nitrocarburizing，简称NC）；复合处理包括先氮化后渗碳（N5%+CE与N3%+CE）以及先铁素体氮碳共渗后渗碳（NC+CE）。本研究所用处理混合气配比如下：氮化处理采用5%N₂+95%H₂与3%N₂+97%H₂两种混合气，渗碳处理采用5%CH₄+95%H₂混合气，铁素体氮碳共渗处理采用5%N₂+1.5%CH₄+93.5%H₂混合气。随后对试样开展微观组织表征，采用光学显微镜、扫描电子显微镜（Scanning Electron Microscopy）结合X射线衍射（X-ray Diffraction，XRD）分析，并辅以显微硬度测试。XRD分析结果显示，所有渗碳处理试样的最表层渗碳体（Cementite）层均趋于稳定；实验结果表明，氮化处理可获得更显著的硬度提升以及更为规整的化合物层，但NC+CE与N5%+CE处理的试样可获得更大的硬化层深度，最大硬化层深度可达800 μm。