316奥氏体不锈钢的等离子体源渗氮

采用不同的工艺参数,包括渗氮气压、试样与活性屏之间的距离和施加于试样的负偏压,对AISI316奥氏体不锈钢进行了等离子体源渗氮,以研究渗氮工艺对AISI 316不锈钢等离子体源渗氮行为的影响。结果表明:(1)当试样带悬浮电位、渗氮气压为300 Pa时,随着试样与活性屏的间距从20 mm增加至200 mm,渗氮层厚度由18μm减小至7μm,峰值氮浓度从25%降低至17%(原子分数,下同);(2)当试样与活性屏的间距为100 mm时,渗氮气压从300 Pa升高至500 Pa,渗氮层厚度从16μm减少至7.5μm,峰值氮浓度从21%下降至18%;(3)当渗氮气压为300 Pa、试样与活性屏间距为100 mm时,对试样施加200 V负偏压,氮层厚度和峰值氮浓度分别从未施加负偏压的15μm和20%提高到了18μm和24%。AISI 316不锈钢等离子体源渗氮效果随试样与活性屏之间距离的增大而变差,适当降低渗氮气压或对试样施加适当的负偏压,均有助于提高AISI 316不锈钢渗氮层的厚度和氮浓度。     

AISI 316L奥氏体不锈钢空心阴极放电离子源渗氮技术

采用双层圆筒不锈钢板组成空心阴极电极结构,作为奥氏体不锈钢渗氮的等离子体源。对AISI 316L奥氏体不锈钢分别进行常规直流离子渗氮和空心阴极等离子体源渗氮处理试验。氮化温度均为450℃,氮化时间为4h。采用X射线衍射仪、金相显微镜、粗糙度仪、显微硬度仪、电化学工作站和摩擦磨损试验机等分析表征氮化试样。结果表明:空心阴极等离子体源渗氮能够有效处理AISI 316L奥氏体不锈钢,可在表面制备5μm厚的γN相氮化层。与传统离子渗氮相比,氮化表面硬度均一,粗糙度较低,特别是边缘效应明显降低。γN相氮化层的耐蚀性能优异,且减摩效果较好。     

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.     

添加合金元素对奥氏体不锈钢等离子渗氮和渗碳的影响

奥氏体不锈钢众所周知有良好的耐蚀性,但是在工业上没有用于承受摩擦的工件上,因为它的硬度低,摩擦磨损性能差。奥氏体不锈钢经低温等离子体渗氮或渗碳能生成一层特殊的氮化物或碳化物层,称为S相,它具有高的硬度和优良的耐蚀性。这项研究中各种奥氏体不锈钢都经低温等离子体渗氮或渗碳,用各种分析技术研究了添加合金元素对S相特性的影响,用了光学显微镜和电子显微镜观察,做了X射线衍射分析,在5%H2SO4溶液中测量阳极极化,用球对平面摩擦装置做摩擦磨损测试。氮化物或碳化物层厚度随处理温度增加而加厚,AISI316钢上生成的渗层厚度是所有的基体钢材中最厚的。超过临界温度,由于氮化铬工碳化铬沉淀使耐蚀性降低。临界温度由渗氮的基材决定。另一方面,在渗碳层中临界温度不随基材变化。大部分样品上S相层的耐蚀性比没有处理的不锈钢的低。但是,AISI316和JIS-SUS304J3钢在400℃渗碳后都有和未处理钢一样优良的耐蚀性。每种不锈钢经渗氮或渗碳后耐磨性都有明显的改进。     

活性屏等离子体源渗氮技术原理及应用

活性屏等离子体源渗氮技术是一种先进的渗氮技术,消除了常规直流等离子体渗氮技术的固有缺陷,且可处理聚合物材料及表面附着氧化皮的金属材料.本文介绍了活性屏等离子体源渗氮技术传质机理的研究进展,在改性低合金钢、不锈钢、工具钢、聚合物材料以及抗菌功能材料等方面的最新结果,评述了活性屏等离子体源渗氮技术存在的问题和发展趋势.     

AISI 300系列奥氏体不锈钢渗氮层组织和性能研究

目的 在AISI 300系列奥氏体不锈钢表面制备单一S相渗氮层,提高该系列不锈钢渗氮层的硬度、抗磨损性能,对比揭示渗氮前后不锈钢的磨损机制。方法 采用低温辉光等离子渗氮技术(LTPNT)在AISI 300系列奥氏体不锈钢表面制备渗氮层。利用光学显微镜(OM)、扫描电子显微镜(SEM)、电子探针(EPMA)、X射线衍射仪(XRD)分析渗氮层的截面形貌、元素分布和物相组成;通过比磨损率和磨痕形貌分析渗氮层的摩擦学性能;利用电化学实验考察渗氮前后3种不锈钢的耐蚀性。结果 AISI 300系列奥氏体不锈钢经380 ℃、12 h处理后,其表面获得了厚度为15 μm左右、与基体致密结合、组织成分均匀的渗氮层;渗氮层的相结构主要为S相,无CrN相析出;经渗氮后,该系列不锈钢表面硬度均为1 100HV左右,较基体硬度提高了5倍左右;不锈钢基体的磨损机理为黏着和磨粒磨损,经渗氮后转变为氧化磨损和微切削;渗氮层的比磨损率约为不锈钢基体的1/20,抗磨损的能力得到显著提升;在25 ℃环境温度下渗氮后,304L、316L和321的自腐蚀电位下降,腐蚀电流密度增加,腐蚀速率加快,耐腐蚀性能稍有降低。通过对比腐蚀形貌发现,渗氮层仍具有一定的耐蚀性能。结论 通过LTPNT可以获得高硬度、组织均匀致密、结合强度高的渗氮层,渗氮层中S相的存在可以显著提高AISI 300系列奥氏体不锈钢的表面硬度、抗磨损能力,降低其摩擦因数和比磨损率,对延长不锈钢的服役寿命有着积极的作用。     

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.     

奥氏体不锈钢渗碳层的组织及耐蚀强化性能研究

针对常规渗碳工艺会削弱奥氏体不锈钢耐蚀性的问题,通过对现有气体渗碳技术进行改进,采用前处理活化、降低渗碳温度的方法,实现了奥氏体不锈钢渗碳兼顾表面强度与耐蚀性能的目标。采用该工艺对AISI304和AISI316奥氏体不锈钢进行渗碳处理,并分析渗层组织和性能,结果表明,在470℃条件下,AISI316不锈钢经气体渗碳处理后,渗碳层具有优异的耐蚀强化性能。     

温度对AISI304奥氏体不锈钢离子渗氮的影响

对AISI304奥氏体不锈钢进行脉冲电流辉光离子渗氮处理,在不同处理温度(480 ℃、520 ℃、580 ℃)下渗氮8 h后,获得了一定厚度的渗氮层.通过对渗层进行金相分析和硬度测试表明,随着渗氮温度升高,渗层厚度增大,显微硬度先增大后减小.综合温度对渗层厚度与显微硬度的影响,AISI304奥氏体不锈钢卡套辉光离子渗氮温度可采用520 ℃,渗氮后渗层厚度为90 μm,显微硬度为1317 HV0.1.     

450℃渗氮AISI 316L不锈钢中膨胀奥氏体的分解

奥氏体不锈钢等离子渗氮时会形成膨胀奥氏体(γN),其强度、韧性和耐蚀性均高于传统的氮化物层。然而,膨胀奥氏体在热力学上是亚稳的,其性能会因其发生分解而降低。本文对AISI 316L不锈钢进行了等离子渗氮,工艺为450℃×5 h,压力500 Pa。对渗氮后试样采用XRD、OM和TEM等进行了显微组织表征。试验结果证明了面心立方膨胀奥氏体的存在,其晶格常数比未经渗氮奥氏体增加多达9.5%。薄片试样的TEM分析表明,N层中有细小的氮化物形成,并且发现一些区域呈奇特的层片状形貌,与碳钢中的珠光体团很相似。选区电子衍射(SAED)分析表明,这些区域由膨胀奥氏体局部分解产生的体心立方铁素体和立方晶系氮化铬组成。在所研究试样中的某些区域,发现有非晶态膨胀奥氏体。N的分解与膨胀奥氏体层局部区域中铁素体稳定元素(Cr,Mo)的显微偏析和奥氏体稳定元素(Ni)的贫化有关。     

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.     

Progress in control of nitriding potential in ASPN process

Abstract

A novel active screen plasma nitriding (ASPN) process provided excellent temperature homogeneity in the load and showed further progress in the control of nitriding potential. In addition to a variation of the nitrogen partial pressure in the process gas commonly used in the conventional plasma nitriding, the applied bias power strongly impacted the nitriding results. In the present work, an application of both methods for the control of nitriding potential in the ASPN process was systematically investigated for a wide range of process parameters to meet the treatment requirements for different types of engineering steel. A two-stage technique based on proper choice of process temperature and required nitriding potential in each stage has been applied in the ASPN process to avoid unnecessary compromises between sufficient thickness of the compound layer, the maximum case hardness and the acceptable nitriding hardness depth.     

富氮层快速离子渗氮工艺及机理研究

利用正交试验法对活性屏快速离子渗氮工艺参数进行优化,并对正交试验预测的优化工艺参数进行了验证。利用Fick第二扩散定律对快速离子渗氮优化工艺的富氮层进行了氮浓度、氮浓度梯度的计算。试验及计算结果表明,高温渗氮温度、高温渗氮时间和低温渗氮时间对渗层厚度的影响较大,选择合适的参数可以在渗氮时间不变、渗层硬度不降低的前提下显著增加渗层厚度。当富氮层厚度为8μm时,采用快速渗氮技术得到试样内表面与基体之间的氮浓度梯度,为传统渗氮模式的20倍以上。     

钢的等离子体基低能离子注入的传质机制

等离子体基低能离子注入是一种钢的低温,低压表面改性方法,它包括等离子体源离子渗氮和等离子体源离子渗碳两种工艺。等离子体基低能离子注入的主要传质机制是低能离子注入－同步热扩散,即在脉冲负偏压作用下的离子首先完成不依赖于工艺温度的低能离子注入,然后已注入的原子在较低的工艺温度上发生足够的热扩散,等离子体热扩散吸收具有补充的传质作用,但由于工艺温度较低,这种作用很小,连续的热扩散过程有利于改善注入吸收条     

Investigation of nitrogen mass transfer within an industrial plasma nitriding system I: The role of surface deposits

It has been proposed that in plasma nitriding, sputtering of material from biased components within the chamber assists in the nitrogen mass transfer process. Here, we investigate the effects of this sputter deposition process on the nitriding response of biased and unbiased AISI P20 steel samples mounted in a large-scale plasma nitriding system operated at 520 °C. Films with nanostructured morphologies resulting from Volmer-Weber film growth were observed on Si substrates placed adjacent to AISI P20 steel substrates after nitriding experiments. Auger depth profiling revealed that the films on the Si substrates had a stoichiometric ratio of 4:1 Fe:N. This suggested that the particles consisted largely of Fe₄N and it was concluded that they were formed from atoms and small clusters sputtered from biased components in the chamber. Despite the deposition of these films, no significant improvement in surface hardness was observed in the steel samples unless bias was applied to them. Furthermore, the maximum hardness achieved in biased P20 samples after the nitriding process occurred in the samples positioned adjacent to the Si samples supporting the thinnest deposited films. These findings do not support the proposition that in plasma nitriding, nitrogen mass transfer occurs predominantly by sputter deposition of iron nitride.     

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。     

等离子体渗氮气压对合金钢渗氮层微观结构和性能的影响

目的 选择M50NiL钢（高合金钢）和AISI 4140钢（低合金钢）2种合金钢,研究渗氮气压对合金钢等离子体渗氮层组织结构、渗层厚度、硬度、韧性和摩擦磨损性能的影响规律。方法 根据离子渗氮GB/T30883—2017,在0～500 Pa渗氮气压范围内选择170、250、350 Pa 3个渗氮气压进行等离子体渗氮,研究渗层微观结构和性能。结果 对于M50NiL和AISI 4140两种合金钢,350 Pa时渗层厚度均最大,170 Pa次之,250 Pa厚度最小。M50NiL钢在350 Pa渗氮和AISI 4140钢在170 Pa渗氮时,表面层具有最优的强韧性。摩擦磨损性能显示,170 Pa和350 Pa气压渗氮的摩擦磨损性能明显优于250 Pa气压渗氮,其中磨损率规律与渗氮层的韧性值测试结果吻合。结论 气压影响了氮离子的能量和分布,从而影响了渗层厚度,钢中的合金元素含量和气压共同影响表面强韧化效果,并且表面强韧化效果直接影响渗氮层的摩擦磨损性能。     

Plasma nitriding of 42CrMo low alloy steels at anodic or cathodic potentials

The nitriding of low alloy steel has been carried out at anodic potential in a space enclosed by an active screen that consists of two cylinders with different diameter. These two cylinders made up a hollow cathode in a discharge system. The difference in diameter of the two cylinders is about 8-10 mm to maintain strong discharge between them. They can also be heated rapidly to the required temperature for treatment. The sample to be nitrided was held at the same potential as that of the anode used in the discharge and heated through heat radiation from the hot cylinders and by electron bombardment. Electrons bombarded the surface of the sample even though the intensity of bombardment was low because of the anodic sheath. To illustrate the effect of the anodic potential on the nitriding a comparison was made between nitriding at anodic and cathodic potential (general plasma nitriding). The phase composition, the compound layer thickness and the surface topography of the nitrided layer, as well as its properties, were investigated using X-ray diffraction, scanning electron microscopy and microhardness tester. In particular, the corrosion properties of the untreated and plasma nitrided samples were evaluated using anodic polarization tests in 3.5% NaCl solution. The results showed that anodic plasma nitriding not only increased the surface hardness but also improved the corrosion resistance of the low alloy steel.     

不锈钢表面含Cu功能梯度复合改性层的制备及抗菌性能

为提高奥氏体不锈钢(ASS)的耐磨性及赋予其抗菌性能,应用改进的活性屏离子渗氮(ASPN)技术,将纯铜冲孔板置于不锈钢冲孔板上面作为活性屏的顶盖,对316奥氏体不锈钢在低温下(430℃)进行表面渗氮处理,在其表面形成由含Cu抗菌沉积层和S相(氮在奥氏体中的过饱和固溶体γ_N)硬质支撑层组成的功能梯度复合改性层。用扫描电镜(SEM)及其所附能谱仪(EDS)、X射线衍射仪(XRD)表征复合改性层的组织形貌、成分及相结构。用显微硬度计和往复摩擦磨损试验机测试了基体和复合改性层的显微硬度和摩擦磨损性能,用金黄色葡萄球菌进行体外抗菌试验评价复合改性层的抗菌性能。结果表明,在偏压达到250 V后,形成了连续分布的硬质S相扩散层和含Cu沉积层组成的复合改性层。改性层表面最高硬度可达928 HV0.05,与Si₃N₄小球对磨时比磨损率较基体降低约57.76%,显著提高了不锈钢的耐磨性。抗菌试验表明,复合改性层与金黄色葡萄球菌接触24 h后,对金黄色葡萄球菌抗菌率提高到98.5%。改进的活性屏离子渗氮技术制备的功能梯度复合改性层可以有效提高...     

直流电场对40Cr钢的低温QPQ催渗

以40Cr作为基体材料,研究了施加直流电场对450 ℃低温QPQ处理时的加速渗氮。对处理后试样的渗层组织、渗层厚度、渗层硬度及物相进行了分析,并对低温QPQ直流电场加速渗氮的机理进行了分析。结果表明:通入直流电场保温2 h后试样的化合物层可达18 μm,与无直流电场保温17 h的化合物层厚度相近,显著提高了渗氮速度。施加直流电场后的40Cr钢表面硬度达到813 HV0.1,是无直流电场硬度的1.3倍。直流电场能够使阳极试样周围聚集CNO^-离子,并为CNO^-离子的分解提供额外能量,获得更多渗氮所需的活性氮原子,从而达到催渗效果。