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首页> 外文期刊>Vacuum: Technology Applications & Ion Physics: The International Journal & Abstracting Service for Vacuum Science & Technology >Repairing the cracks network of hard chromium electroplated layers using plasma nitriding technique
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Repairing the cracks network of hard chromium electroplated layers using plasma nitriding technique

机译：用等离子渗氮技术修复镀硬铬层的裂纹网络

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摘要

The use of hard chromium electroplated coatings for industrial and decorative applications is widespread. However, there seem to be some defects like the existence of an extensive micro-cracks network that restrict their applications. They affect corrosion resistance due to formation of direct routes to the substrate through which corrosive agents could reach the main metal. Plasma nitriding process is proved an effective technique to overcome such problems. The objective of this study is to investigate the effect of plasma nitriding parameters namely, time and temperature, on the closure of the cracks. Samples of a hard chromium electroplated hot work tool steel were heat-treated via conventional plasma nitriding (CPN) and active screen plasma nitriding processes (ASPN) at 500 and 550 degrees C for 5 and 10 h, and at 550 and 600 degrees C for 10 and 15 h, respectively. The morphology and microstructure of the samples were characterized by the scanning electron microscopy (SEM) imaging. The coating phases were determined by the X-ray diffraction (XRD) method. The corrosion properties of samples were evaluated using anodic polarization tests in a 3.5 wt% NaCl solution at 25 degrees C. The results showed that both techniques filled up the cracks. However, the closure mechanisms were different. In CPN method, the cracks were disappeared due to the transformation of chromium to its nitrides, which occur with volume expansion. It is worth noting that this phenomenon occurs at lower temperatures and shorter times compared to ASPN method. In ASPN method, the iron nitrides detached from active screen were deposited inside the cracks to fill them up. Moreover, it was found that the corrosion resistances of the samples modified by the CPN process were superior to the ASPN samples. (C) 2016 Elsevier Ltd. All rights reserved.
机译：硬铬电镀涂料广泛用于工业和装饰领域。但是，似乎存在一些缺陷，例如存在限制其应用的广泛的微裂纹网络。由于会形成直接到达基材的路径，因此腐蚀剂会腐蚀腐蚀剂，腐蚀剂可通过这些路径到达主要金属。等离子体氮化工艺被证明是克服此类问题的有效技术。这项研究的目的是研究等离子渗氮参数（时间和温度）对裂纹闭合的影响。通过常规等离子渗氮（CPN）和有源筛分等离子渗氮工艺（ASPN）在500和550摄氏度，5到10摄氏度，550和600摄氏度，分别为10和15小时。样品的形貌和微观结构通过扫描电子显微镜（SEM）成像进行表征。涂覆相通过X射线衍射（XRD）方法确定。在25％的温度下，在3.5 wt％的NaCl溶液中使用阳极极化测试评估了样品的腐蚀性能。结果表明，两种技术都可以填满裂纹。但是，关闭机制不同。在CPN方法中，裂纹由于铬向其氮化物的转变而消失，而铬则随着体积膨胀而发生。值得注意的是，与ASPN方法相比，此现象发生在较低的温度和较短的时间。在ASPN方法中，从有源筛网脱离的氮化铁沉积在裂缝内部，以将其填满。此外，发现通过CPN工艺改性的样品的耐腐蚀性优于ASPN样品。 （C）2016 Elsevier Ltd.保留所有权利。

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