AISI 316不锈钢表面银氮复合共渗及其磨损和抗菌性能

为提高奥氏体不锈钢的表面硬度和耐磨性并赋予其良好的抗菌性能,应用改进的活性屏离子渗氮技术(ASPN)对AISI 316不锈钢进行了银氮(Ag-N)共渗处理。用SEM、EDS、XRD、TEM、辉光放电光谱仪(GDOES)表征复合共渗层的成分和组织结构。对不锈钢基体(SS)和复合共渗层的显微硬度、空气和腐蚀介质中的磨损性能、抗腐蚀性能以及对金黄色葡萄球菌(S.aureus)的抗菌性能进行了分析。结果表明,Ag-N复合共渗处理后形成的复合共渗层连续致密,主要由Ag掺杂S相纳米结构沉积层和S相扩散层构成。复合共渗层表面硬度较基材提高了约3~4倍,干摩擦条件下的磨损量较基体最高降低了约84.6%。复合共渗处理后试样在人工模拟体液(SBF)中的耐蚀性较基体不锈钢略有降低,比磨损率较基体降低了约35%。抗菌试验表明,复合共渗层与金黄色葡萄球菌(S.aureus)接触12 h后,达到了100%的杀菌率。     

表面织构-等离子氮化复合处理316不锈钢的液体润滑摩擦学性能

针对316不锈钢表面承载能力低、耐磨性差等问题,采用磨料水射流对316不锈钢进行喷丸处理获得表面凹槽织构,再对表面织构316不锈钢进行了等离子渗氮二次处理,获得了表面织构-离子氮化表面复合改性层。利用SEM、EDS、超景深形貌系统和摩擦磨损仪分析了316不锈钢基体(316SS)、渗氮316不锈钢(PN-316SS)、织构化316不锈钢(ST-316SS)、织构-渗氮316不锈钢(ST-PN-316SS)在液体润滑条件下与Si3N4陶瓷球配副对磨的摩擦学行为。结果表明:在整个滑动过程中,4种试样表现出不同的磨损机理,从磨损量、摩擦因数以及磨损表面特点来看,ST-PN-316SS耐磨性优于其它单一表面改性试样的耐磨性,起到了降低磨损、连续提供润滑的作用,其磨损机理主要为轻微的塑性变形与氧化磨损。     

AISI304奥氏体不锈钢阳极渗氮层的组织与摩擦磨损性能

为避免传统直流离子渗氮存在的表面打弧和边缘效应等弊端,采用活性屏阳极渗氮法对AISI 304奥氏体不锈钢进行表面处理。将样品放置于阳极电位,在440~520℃范围内,渗氮处理8 h。分析了渗氮层的微观组织结构与形貌,并考察了渗氮前后的摩擦磨损性能。结果表明:在低温440℃下,在表面制备了高硬度的S相强化层。XRD与TEM表明S相为面心立方结构,且无Cr N相析出。高温520℃渗氮表面硬度值(1100 HV0.1)是基体的5倍,但Cr N相明显析出。在干摩擦条件下,渗氮处理后的摩擦系数在0.8左右,相对渗氮前降低约0.2,特别是磨损率只有渗氮前的十分之一量级。磨损机制从原始基体的严重粘着转变为轻微的氧化和磨粒磨损。     

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。     

气压对304奥氏体不锈钢低温离子渗氮组织与性能影响

在400℃、8 h、不同气压(80~400 Pa)条件下对304奥氏体不锈钢进行离子渗氮处理。采用扫描电镜(SEM)、X射线衍射仪、显微硬度计及万能摩擦试验机对表面改性后的304奥氏体不锈钢渗层组织、相结构、渗层硬度以及耐磨性进行了测试和分析。结果表明,400℃离子渗氮处理后304奥氏体不锈钢形成了明显的白亮层,即单相S相层;低压对304奥氏体不锈钢离子氮化具有良好的催渗效果,即渗层厚度随气压的减小而增加,在100 Pa条件下,渗层厚度达到最大值51.7μm;渗氮后试样表面硬度达到最大值1100 HV0.01;低温低压离子渗氮能够提高304奥氏体不锈钢耐磨性,80 Pa和100 Pa是提高304奥氏体不锈钢耐磨性的最佳气压。     

离子渗氮和固溶复合处理制备深层含氮奥氏体不锈钢

目的 通过离子渗氮和固溶复合处理制备深层含氮奥氏体不锈钢,获得硬度、耐蚀性和耐磨性等综合性能优良的奥氏体不锈钢。方法 将304奥氏体不锈钢试样放在LD-8CL型直流等离子体渗氮炉内,在400 Pa下进行560 ℃、4 h的离子渗氮处理,渗氮后进行1050 ℃、8 h的固溶处理。使用HXD-1000TMC型显微硬度计、DMI-3000M型金相显微镜、D/max-2500型X射线衍射仪（XRD）、Thermo250XI型X射线光电子能谱仪（XPS）、CS 350电化学测量系统和万能摩擦磨损试验机,对经过复合处理的304不锈钢的截面硬化梯度、截面组织、物相、表面成分、耐蚀性和耐磨性进行研究分析,验证此复合处理对获得硬度高、耐蚀性和耐磨性好等综合性能优良的奥氏体不锈钢的适用性。结果 经过复合处理,不锈钢表面的氮原子数分数为1.56 %,且为单一奥氏体相?N。?N所对应的衍射峰相对于不锈钢基体向左偏移,有效硬化层深达1.0 mm,不锈钢的表面硬度从基体的210HV0.025提高到308HV0.025。不但提高了深层含氮奥氏体不锈钢的耐磨性,而且提高了不锈钢的耐蚀性,腐蚀电位从基体的-0.534 V提高到-0.422 V,摩擦系数由基体的0.8降到0.7。结论 离子渗氮和固溶复合处理适用于制备综合性能优良的深层含氮奥氏体不锈钢。工艺设计时,可以根据材料服役要求,选择合适的固溶工艺,从而获得满足不同综合性能要求的含氮不锈钢。     

双相不锈钢等离子表面硬化技术的进展

双相不锈钢兼具奥氏体和铁素体不锈钢的特点，塑性和耐蚀性好，但硬度低，耐磨性差。等离子表面硬化处理能提高双相不锈钢的表面硬度和耐磨性，包括离子渗氮、直流辉光等离子渗氮、活性屏等离子渗氮、空心阴极辅助离子渗氮、等离子沉积薄膜(物理气相沉积、化学气相沉积)、等离子热喷涂、离子注入以及表面复合处理等。     

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。     

AISI304不锈钢表面渗Cu层对其摩擦学行为的影响

利用等离子表面合金化技术,在304不锈钢表面制备渗Cu改性层。借助球-盘磨损试验机对改性层常规大气环境下与不同偶件（GCr15球,Al2O3球）对摩时的摩擦学性能进行了测试。结果表明：不锈钢表面渗Cu改性层均匀致密、与基体结合良好,厚度大约26μm,主要由纯Cu和膨胀的奥氏体等相组成。渗Cu改性层的摩擦学性能与摩擦偶件相关。渗Cu不锈钢与GCr15球对摩时Cu改性层阻止了不锈钢与配副直接接触,并在摩擦过程中起到固体润滑作用,明显改善了不锈钢的摩擦学性能;渗Cu不锈钢与Al2O3球对摩时,由于陶瓷球的稳定化学性能及Cu改性层相对较低的剪切强度,导致摩擦过程中磨粒磨损加剧。     

304奥氏体不锈钢低气压离子渗氮组织与性能研究

在400℃、低气压下对304奥氏体不锈钢进行低温低压离子渗氮处理。采用扫描电镜、显微硬度计及万能摩擦试验机对表面改性后的304奥氏体不锈钢渗层组织、硬度及耐磨性进行了测试和分析。结果表明:304奥氏体不锈钢低温低气压渗氮形成了明显的白亮层;低气压对304奥氏体不锈钢离子渗氮具有良好的催渗效果,即渗层厚度随气压的减小而增加,在100 Pa条件下,渗层厚度达到最大值51.7μm;渗氮后试样表面硬度达到最大值1100 HV0.01;低温低气压离子渗氮能够提高304奥氏体不锈钢耐磨性,80 Pa和100 Pa是提高304奥氏体不锈钢耐磨性的最佳气压。     

渗扩时间比对AISI 316不锈钢渗氮层组织与性能的影响

采用真空两段渗氮工艺,在不同的强渗、扩散时间下对AISI 316不锈钢进行渗氮处理,通过X射线衍射(XRD)、扫描电镜(SEM)、光学显微镜(OM)、显微硬度测试和摩擦磨损试验等分析了渗氮层的组织和性能。结果表明,经过12 h的真空渗氮后,AISI 316不锈钢表面形成了一层由γ′-Fe₄N、ε-Fe_2-3N和CrN等相组成的渗氮层,其表面硬度和耐磨性能相较于基体均有明显的提高。其中,渗扩时间比为1∶1(强渗6 h、扩散6 h)时的渗层厚度约为96 μm,表面硬度约为1069 HV0.5,是基体表面硬度的4.5倍,在20 N载荷下的磨损量约为基体的1/3;渗扩时间比为1∶2(强渗4 h、扩散8 h)时的渗层厚度约为120 μm,ε-Fe_2-3N相衍射峰增强,在20 N载荷下的磨损量约为基体的1/30。延长扩散时间能增加渗氮层厚度,改善表面形貌,进一步提高不锈钢的耐磨性。     

Duplex surface treatment of an AISI 316L stainless steel; microstructure and tribological behaviour

Austenitic stainless steel AISI 316L is used in several industrial applications, mainly due to its excellent corrosion resistance; however, its low hardness and poor wear performance impose strong limitations in many cases. A combination of DC-pulsed plasma nitriding and plasma assisted PVD coating as a surface treatment has been shown to improve the material fatigue and wear resistance without affecting the corrosion performance. In the present work a duplex treatment, consisting of a plasma nitriding at 673 K for 20 h and a subsequent coating with a TiN layer was applied to an AISI 316L steel. The microstructure obtained as well as the tribological behaviour was extensively studied. Wear tests were performed in rolling-sliding condition under different loads (490, 1225 and 1960 N). Different wear mechanisms were observed depending on the normal applied load. Analysis and discussion of the wear test results showed that the combination of the two processes, plasma nitriding and plasma assisted PVD coating, improves considerably the wear resistance of the AISI 316L. At low applied loads, the duplex treatment improved significantly the wear resistance during the sliding/rolling contact, i.e. only abrasion was observed. However, upon increasing the applied loads fatigue and delamination wear mechanism appeared. In the case of the highest applied load, delamination was the main wear mechanism observed in the tested samples.     

AISI316 不锈钢表面等离子渗硼及摩擦磨损性能的研究

目的改善AISI316不锈钢的摩擦磨损性能。方法采用双辉等离子合金化技术,以块状Fe B化合物作为源极材料,在AISI316不锈钢表面制备含硼改性层,对渗层组织、成分、相结构和显微硬度进行分析,并研究改性层在干摩擦条件下的摩擦磨损性能。结果经渗硼处理后,AISI316不锈钢表面形成了一层连续、致密、均匀的改性层,主要由Mo2B和Fe B相组成。改性层具有较高的硬度(964HV0.1),较基体硬度提高了约3倍,且耐磨性较基体有明显提高。结论通过在AISI316不锈钢表面制备渗硼改性层,可明显提高基体材料的硬度和摩擦磨损性能。     

Corrosion resistance properties of glow-discharge nitrided AISI 316L austenitic stainless steel in NaCl solutions

Glow-discharge nitriding treatments can modify the hardness and the corrosion resistance properties of austenitic stainless steels. The modified layer characteristics mainly depend on the treatment temperature. In the present paper the results relative to glow-discharge nitriding treatments carried out on AISI 316L austenitic stainless steel samples at temperatures ranging from 673 to 773 K are reported. Treated and untreated samples were characterized by means of microstructural and morphological analysis, surface microhardness measurements and corrosion tests in NaCl solutions. The electrochemical characterization was carried out by means of linear polarizations, free corrosion potential-time curves and prolonged crevice corrosion tests. Nitriding treatments performed at higher temperatures (>723 K) can largely increase the surface hardness of AISI 316L stainless steel samples, but decrease the corrosion resistance properties due to the CrN precipitation. Nevertheless nitriding treatments performed at lower temperatures (?723 K) avoid a large CrN precipitation and allow to produce modified layers essentially composed by a nitrogen super-saturated austenitic metastable phase (S-phase) that shows high hardness and very high pitting and crevice corrosion resistance; at the same polarization potentials the anodic current density values are reduced up to three orders of magnitude in comparison with untreated samples and no crevice corrosion event can be detected after 60 days of immersion in 10% NaCl solution at 328 K.     

Corrosion properties of active screen plasma nitrided 316 austenitic stainless steel

AISI 316 austenitic stainless steel has been plasma nitrided using the active screen plasma nitriding (ASPN) technique. Corrosion properties of the untreated and AS plasma nitrided 316 steel have been evaluated using various techniques, including qualitative evaluation after etching in 50%HCl + 25%HNO₃ + 25%H₂O, weight loss measurement after immersion in 10% HCl, and anodic polarisation tests in 3.5% NaCl solution. The results showed that the untreated 316 stainless steel suffered severe localised pitting and crevice corrosion under the testing conditions. AS plasma nitriding at low temperature (420 °C) produced a single phase nitrided layer of nitrogen expanded austenite (S-phase), which considerably improved the corrosion properties of the 316 austenitic stainless steel. In contrast, AS plasma nitriding at a high temperature (500 °C) resulted in chromium nitride precipitation so that the bulk of the nitrided case had very poor corrosion resistance. However, a thin deposition layer on top of the nitrided case, which seems to be unique to AS plasma nitriding, could have alleviated the corrosion attack of the higher temperature nitrided 316 steel.     

Surface nanocrystallization by surface mechanical attrition treatment and its effect on structure and properties of plasma nitrided AISI 321 stainless steel

A plastic deformation surface layer with nanocrystalline grains was produced on AISI 321 austenitic stainless steel by means of surface mechanical attrition treatment (SMAT). Low-temperature nitriding of SMAT and un-SMAT AISI 321 stainless steel was carried out in pulsed-DC glow discharge. The effect of SMAT pretreatment on the microstructure and properties of the stainless steel were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Vickers hardness tester and UMT-2MT tribometer. The results show that the plasma nitriding of AISI 321 steel can be enhanced considerably by means of SMAT process before nitriding, and a much thicker nitrogen diffusion layer with higher hardness was obtained for the SMAT samples when compared with un-SMAT samples. In addition, the wear resistance and load capacity of the nitrided layers on the SMAT samples was much higher than that of the un-SMAT samples due to the thicker S phase case and the gradient nitrogen diffusion layer.     

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.     

Improvement of Mechanical Properties of Martensitic Stainless Steel by Plasma Nitriding at Low Temperature

A series of experiments were carried out to study the influence of low temperature plasma nitriding on the mechanical properties of AISI 420 martensitic stainless steel. Plasma nitriding experiments were carried out for 15 h at 350℃ by means of DC- pulsed plasma in 25%N2＋ 75%H2 atmosphere. The microstructure, phase composition, and residual stresses profiles of the nitrided layers were determined by optical microscopy and X-ray diffraction. The microhardness profiles of the nitridied surfaces were also studied. The fatigue life, sliding wear, and erosion wear loss of the untreated specimens and plasma nitriding specimens were determined on the basis of a rotating bending fatigue tester, a ball-on-disc wear tester, and a solid particle erosion tester. The results show that the 350℃ nitrided surface is dominated by c-Fe3N and ON, which is supersaturated nitrogen solid solution. They have high hardness and chemical stabilities. So the low temperature plasma nitriding not only increases the surface hardness values but also improves the wear and erosion resistance. In addition, the fatigue limit of AISI 420 steel can also be improved by plasma nitriding at 350℃ because plasma nitriding produces residual compressive stress inside the modified layer.     

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。