偏压对45钢离子渗氮行为的影响

在直流脉冲等离子体渗氮炉内放置一由双层圆筒组成的活性屏,双层圆筒与阴极相接,由于其直径不同可以产生空心阴极放电.将45钢试样放置在活性屏内,一组试样处于悬浮状态,另一组试样施加负偏压(-50～-150 V),同时在400～550℃下进行离子渗氮处理.并用金相显微镜、XRD和显微硬度计对渗氮层进行对比分析.结果表明:偏压显著影响渗氮层的组织结构和性能.偏压试样渗氮层与悬浮试样相比,具有更厚的化合物层,表面硬度更高,扩散层更厚.     

纯氮气氛活性屏离子渗氮的研究

在纯氮气氛中，利用活性屏离子渗氮(ASPN)技术对38CrMoAl钢进行了离子渗氮处理，并对渗层的组织结构、硬度、深度等进行了分析。结果表明，只有直流辉光放电电压高于800V时，在纯氮气氛中才能进行活性屏离子渗氮处理。通过对等离子放电空间的粒子进行XRD分析发现，放电电压低于800V时，沉积在基材表面的粒子主要是氧化铁(Fe3O4)；放电电压高于800V时，沉积在基材表面的粒子才是能进行活性屏离子渗氮处理的铁的氮化物(ε，γ‘)。     

高速钢的活性屏离子渗氮

利用活性屏离子渗氮技术对W18Cr4V高速钢进行渗氮处理,对其组织、硬度和渗层深度进行分析,并与普通直流离子渗氮作比较.结果表明,经活性屏离子渗氮处理后.渗氮层硬度梯度变得平缓.且最高硬度不在表面,而是在距表面一定距离处,这将能提高高速钢的耐疲劳性能,改善高速钢的内在质量.     

工件电位对奥氏体不锈钢活性屏离子渗氮的影响

用活性屏离子渗氮技术分别对处于悬浮电位和阳极电位的AISI 316L奥氏体不锈钢进行低温渗氮处理.并对渗氮层的组织、形貌、相结构、显微硬度和耐蚀性能进行分析.结果表明,在这两种电位状态下处理的试样均可获得具有S相结构特征的单相硬化层.渗氮层不仅具有高的硬度,还有良好的耐蚀性能.在活性屏离子渗氮过程中,从活性屏上溅射下来的中性S相粒子也可以起到氮载体的作用.活性屏空间中性粒子和电子的撞击足以消除不锈钢表面钝化膜对氮的阻隔作用.     

渗氮温度对奥氏体不锈钢性能的影响

利用自行研制的直流脉冲离子渗氮设备对奥氏体不锈钢进行离子渗氮,采用显微硬度计、倒置金相显微镜等手段研究了渗氮温度对奥氏体不锈钢显微硬度、金相组织、耐磨性能和耐腐蚀性能的影响.结果表明,通过离子渗氮处理得到的渗层表面硬度均在1150 HV0.05以上,耐磨性能提高4～5倍,低温离子渗氮在提高耐磨性能的同时保持其耐腐蚀件能基本不变.     

纯氮气氛下活性屏离子渗氮处理及其影响因素

利用活性屏离子渗氮(ASPN)技术对38CrMoAl钢在纯氮气氛下进行离子渗氮处理,对渗氮层的硬度、深度、组织结构以及收集粒子的形貌、结构等进行了分析研究.结果表明,电压较低时,Fe主要与O结合生成大量的氧化铁而不能进行ASPN处理,氧起主导作用;只有在电压较高、Fe与N的结合能力较强时才主要生成吸附大量活性氮原子的氮化铁进行ASPN处理.     

装炉方式对40CrNiMo钢离子渗氮表面粗糙度的影响

将初始组织状态相同、表面粗糙度R_a为0. 1μm的40CrNiMo试样,分别放置在距阳极不同距离的碳钢圆筒内外进行离子渗氮。随后利用光学显微镜、显微硬度计和三维表面形貌测量系统测定渗氮后各试样的表面硬度、渗层深度、显微组织及表面粗糙度。结果发现:各试样的表面硬度和渗层深度无明显差别,渗氮层显微组织也无明显区别。但渗氮后各试样表面粗糙度却有较明显的差别:当试样放置在圆筒外,距离阳极越远表面粗糙度越高;距阳极距离相同时,置于碳钢圆筒中的试样的表面粗糙度比置于筒外的试样小的多。渗氮层表面粗糙度的降低有利于降低零件的缺口敏感性,提高零件的疲劳性能。     

离子溅射在奥氏体不锈钢离子渗氮中的应用

利用自制的直流脉冲离子渗氮设备采用加强离子溅射预处理方法对奥氏体不锈钢进行了离子渗氮,并与普通的离子渗氮方法进行对比.结果表明,通过加强溅射的方法得到的试样表面硬度在1 200 HV0.5以上,耐磨性能提高了4～5倍,硬度梯度变得更为平缓.     

40Cr钢富氮层快速离子渗氮技术的探索

用活性屏离子渗氮(ASPN)技术对40Cr钢进行快速离子渗氮技术的研究.本项研究是利用氮在奥氏体与铁素体中分别具有不同的溶解度和扩散速度的特性,采用了在共析温度以上短时间溶氮和在共析温度以下长时间扩散渗氮的两种不同的渗氮机制,进行交替渗氮处理.试验结果表明,采用这种新的渗氮工艺不仅可以显著提高渗氮处理中氮在钢中的内扩散速度,而且渗氮层具有较高的硬度.这种快速渗氮工艺可以用"吸收-扩散"渗氮模型进行解释.     

活性屏与工件的距离对40Cr钢活性屏离子渗氮行为的影响

为提高40Cr钢的抗磨及耐蚀性能,用304不锈钢冲孔板制成的活性屏对40Cr钢进行离子渗氮(ASPN)处理,研究了活性屏与工件的距离对渗层组织结构和性能的影响,并与普通直流离子渗氮(DCPN)进行了比较。用光学显微镜(OM)、X射线衍射仪(XRD)、辉光放电光谱仪(GDOES)、显微硬度计、往复摩擦磨损试验机和电化学工作站对渗层组织、相成分、硬度、耐磨及耐腐蚀性能进行分析。结果表明:经不锈钢活性屏离子渗氮处理后,试样表面得到了致密均匀的渗氮层,渗层主要由ε-Fe2-3N、γ′-Fe4N和CrN相组成,且随着试样与活性屏距离从10mm、20mm增加到30mm,对应的渗层厚度从6μm、4.7μm减小到3.5μm。经氮化处理后,40Cr钢的耐磨性和耐腐蚀性都有显著的提高,ASPN处理后试样的耐腐蚀性较DCPN有明显的提高。     

Study on the active screen plasma nitriding and its nitriding mechanism

The active screen plasma and DC plasma nitriding of the low alloy steel 722M24 are investigated. Experimental results showed that the metallurgical characteristics and hardening effect on 722M24 steel nitrided by AS plasma nitriding at both floating potential and grounded potential were similar to those nitrided by DC plasma nitriding. Particles sputtered from the active screen and deposited on the specimen surface play the role of the nitrogen carrier in AS plasma nitriding. XRD and high-resolution SEM analysis indicated that the particles with sizes in sub-micron scale were Fe_xN (x > 2). Based on metallurgical analysis and Optical Emission Spectrometer (OES) experimental results, an AS plasma nitriding model has been proposed considering that AS plasma nitriding is a multi-stage process, involving sputtering, physical adsorption, desorption, diffusion and deposition.     

Study of the Active Screen Plasma Nitriding

Active screen plasma nitriding (ASPN) is a novel nitriding process, which overcomes many of the practical problems associated with the conventional DC plasma nitriding (DCPN). Experimental results showed that the metallurgical characteristics and hardening effect of 722M24 steel nitrided by ASPN at both floating potential and anodic (zero) potential were similar to those nitrided by DCPN. XRD and high-resolution SEM analysis indicated that iron nitride particles with sizes in sub-micron scale were deposited on the specimen surface in AS plasma nitriding. These indicate that the neutral iron nitride particles, which are sputtered from the active screen and transferred through plasma to specimen surface, are considered to be the dominant nitrogen carder in ASPN. The OES results show that NH could not be a critical species in plasma nitriding.     

材料的活性屏等离子渗氮

近年来,等离子渗氮技术的迅速发展和在表面工程领域的应用呈现出减缓的趋势,其原因是传统的直流等离子体技术存在一些固有的缺点,例如,炉温难以保持均匀,等离子体不够稳定以及因打弧而引起工件表面损伤等。克服这些不足之处的努力促使了活性屏等离子渗氮(ASPN)技术的发展。本文从技术和环境优势角度证明,ASPN可以应用于低合金钢、工具钢、不锈钢以及能进行传统直流等离子渗氮的其他钢种。此外,ASPN可以处理不适合直流等离子渗氮的非导电材料,如经氧化处理的钢和高分子材料。从长远看,对环境友好且技术先进的等离子渗氮比传统的盐浴和气体渗氮更有优势。活性屏等离子渗氮技术是充分发挥等离子体技术在化学热处理及有关表面工程中应用潜力的新方法。     

Differences in nitrided layer between classic active screen plasma nitriding and active screen plasma nitriding with hemispherical cathodic cage

Abstract

Active screen plasma nitriding (ASPN) is commonly used when regular surface hardening is necessary. The ASPN technique produces a more homogeneous surface coating than direct current plasma nitriding (DCPN) due to different process principles. The term active screen in plasma nitriding refers to a cathodic cage with a defined geometry. The purpose of this work was to study the differences between ASPN using a hemispherical cathodic cage and ASPN using a normal cylindrical cathodic cage. Following some trials using similar parameters, the tests were carried out with three conditions: with DCPN, with a cylindrical cathodic cage in ASPN and with a hemispherical cathodic cage in ASPN. X-ray diffraction and scanning electron microscopy analysis together with energy dispersive spectroscopy were applied to characterise the nitrided layers. The nitrided layers are not the same for each of the conditions used. The ASPN with a hemispherical cathodic cage produced a layer of almost Fe₃N alone, while the other processes gave significant amounts of Fe₄N in the nitrided layer. Scanning electron microscopy analysis showed different surface morphology for each condition.     

离子渗氮新技术的研究现状

为了克服传统离子渗氮的一些固有缺点，近些年来出现一些新的离子渗氮技术，如活性屏离子渗氮、等离子体源离子渗氮、离子注入离子渗氮等，本文简要介绍了这些新技术及其原理、特点，总结了这类技术的共性模型。其中，活性屏离子渗氮技术和等离子体源离子渗氮技术有着明显的设备和工艺优势，可能成为离子渗氮技术的发展方向。     

活性屏等离子体源渗氮工艺特性及传质机制

为揭示活性屏等离子体源渗氮工艺特性（试样偏压电位和试样距屏高度）对AISI 316奥氏体不锈钢渗氮效果的影响规律,利用最小二乘法线性回归拟合了不同工艺条件下渗氮层厚度数据,绘制了活性屏等离子体源渗氮AISI 316奥氏体不锈钢的工艺特性图,以此确定其最佳工艺参数。并通过对金属网屏上溅射颗粒的化学成分和相结构分析,探讨了活性屏等离子体源渗氮的传质机制。结果表明：渗氮层厚度随试样距屏高度增大而降低,当适当降低渗氮气压或试样施加一定负偏压时,均有助于提高渗氮层的厚度,并且证实了"溅射-再沉积"模型是活性屏等离子体源渗氮重要的传质机制。     

Formation of Ti-N graded bioceramic layer by DC hollow-cathode plasma nitriding

Ti-N graded ceramic layer was formed on titanium by using DC hollow-cathode plasma nitriding technique. The structure of Ti-N layer was analyzed using X-ray diffractometry(XRD) with Cu Kα radiation, and the microhardness( HV0.1) was measured from the surface to inner along the cross section of Ti-N layer. The results indicate that the Ti-N graded layer is composed of ε-Ti2 N, δ-TiN and α-Ti(N) phases. Mechanism discussion shows that hollow-cathode discharge can intensify gas ionization, increase current density and enhance the nitriding potential, which directly increases the thickness of the diffusion coatings compared with traditional nitriding methods.     

Investigation of nitrogen mass transfer within an industrial plasma nitriding system II: Application of a biased screen

Active screen plasma nitriding (ASPN) was conceived in order to reduce negative effects observed in direct current plasma nitriding arising from the application of bias to the components. The mechanism of nitrogen mass transfer in ASPN is still not fully understood. Here, we compare the microstructure, composition and hardness response of AISI P20 and H13 steels after nitriding. A set of samples was nitrided with sample bias applied directly and another set was nitrided at floating potential under an active screen. Similar nitrogen content and hardness profiles were obtained for the samples treated using a bias and under an active screen separated from the samples by 12 mm. When the sample-screen separation was increased from 12 to 70 mm the hardness response improved. The principle processes occurring during ASPN are proposed based on the experimental results. In ASPN, a flux of energetic nitrogen species is generated by the active screen which, provided that the samples are within the range of the energetic species, bombards the surface of the samples being treated. This flux is critical in establishing a nitrogen potential and a satisfactory response in the components.     

40Cr钢循环离子渗氮工艺及渗层硬度研究

目的探索循环离子渗氮与常规恒温离子渗氮技术的工艺效果。方法先对试样进行调质处理,分组进行离子渗氮,固定氨气和乙醇的流量,改变渗氮时间和渗氮温度两种工艺参数及渗氮工艺,分别测定渗氮后各试样的表面硬度及渗层厚度,观察其金相组织,并分析每组试样渗氮层的性能。结果循环离子渗氮530 6 h℃试样的表面硬度最高,随着渗氮温度的升高和渗氮时间的延长,试样的表面硬度增加,但是当温度超过530℃、时间超过6 h后,试样的表面硬度反而降低。循环渗氮550 10 h℃试样的渗层厚度最厚,随着渗氮温度的升高和渗氮时间的增加,试样的渗层厚度变厚,但时间超过6 h后,渗层厚度的增加较缓慢,6、8、10 h试样的渗层厚度差别不大。相同的渗氮温度下,循环渗氮6 h的试样的渗层厚度基本与常规恒温渗氮10 h试样的渗层厚度一样,相同渗氮时间内,循环渗氮510℃的试样的表面硬度高于恒温渗氮550℃试样的表面硬度,且两者的渗层厚度相差不多。结论循环离子渗氮工艺优于常规的恒温离子渗氮,循环离子渗氮550 8 h℃试样的综合性能最好。