氮化温度对24Cr2Ni4MoV钢离子氮化显微组织的影响

为了提高24Cr2Ni4MoV钢零件的表面硬度和耐磨性,对24Cr2Ni4MoV钢进行了离子氮化工艺试验研究,应用光学显微镜和扫描电子显微镜等仪器对520,550,570℃共3个温度离子氮化试样的显微组织、氮化层深度、表面硬度、表面渗氮层脆性、脉状组织等进行了检测分析,并应用能谱仪对渗氮层中氮化物成分进行了分析。结果表明:24Cr2Ni4MoV钢具有良好的氮化效果,其最佳离子氮化温度为550℃;试样在550℃氮化后,不仅氮化层的各项性能均满足标准技术要求,而且提高了渗氮速率,缩短了渗氮时间。     

铝合金离子渗氮层的组织结构研究

研究了离子氮化工艺参数对Ｌ２和ＬＹ１２二种铝合金渗氮层的组织和结构的影响。应用ＳＥＭ，Ｘ－射线衍射分析，ＸＰＳ和ＴＥＭ等方法对渗氮层的组织、相结构、渗氮层的化学成分与价态进行了分析。结果表明，渗氮层由Ａ１Ｎ和含Ｎ的α－Ａｌ固溶体及微量的Ａｌ２Ｏ３所组成。随着离子氮化温度和时间的提高，渗氮层的厚度随之增加。     

稀土催渗对耐蚀氮化的影响

针对Q235钢采用常规气体氮化,其耐腐蚀性能日渐不能适应工程应用要求的问题,探索了添加稀土催渗剂对Q235钢进行稀土催渗氮化的方法.详细研究了渗氮工艺对氮化层厚度的影响.测量了渗氮试样表层硬度沿渗层深度的分布及耐蚀性能与渗氮工艺的定量关系.所有实验与观察均为稀土与常规2种渗氮试样在相同条件下平行操作并做对比分析.采用X光荧光谱仪测量了渗层稀土元素的分布.用X射线衍射仪测量了渗层的相组成.用金相显微镜观察了2种渗氮试样的显微组织.研究结果得出,稀土催渗氮化比常规氮化显著增加了氮化层的厚度,其显微硬度与耐腐蚀性能大幅提高.600℃下渗氮2 h为最适宜的稀土氮化条件.     

液体渗氮工艺对CrNiMo钢渗层厚度和硬度的影响

为了探讨无毒液体渗氮工艺对CrNiMo钢渗层的效果,采用正交试验方法研究了氮化温度、氮化时间和尿素添加量对CrNiMo钢液体渗氮层的脆性、渗层厚度和硬度的影响.结果表明,尿素添加量是影响渗层脆性和硬度的主要因素,氮化时间是影响渗层厚度的主要因素,氮化温度对渗层厚度和硬度的影响较小.最优渗氮工艺为570℃,氮化时间5 h,尿素添加量为50 g/h,此时渗层厚度为0.235mm,最高硬度为920HV,脆性级别为1级.     

铝合金离了渗氮层的组织结构研究

研究了离子氮化工艺参数对Ｌ２和ＬＹ１２二种名合金渗氮层的组织和结构的影响。应用ＳＥＭ，Ｘ－射线衍射分析，ＸＰＳ和ＴＥＭ等方法对渗氮层的组织，相结合渗氮层的化学成分与价态进行了分析。     

阀门阀杆的抗蚀氮化

经抗蚀渗氮后的碳钢、低合金钢及铸铁零件具有良好的抗腐蚀性能,可代替铜件和镀铬件。从氮化抗蚀机理,最佳工艺规范的选择及渗氮层抗恂性的检测等方面探讨了阀门中的重要部件－－阀杆的抗蚀氮化工艺。     

不锈耐热钢制件渗氮层缺陷分析

分析了4Cr14Ni14W2Mo钢制件经一般气体氮化后的渗氮层裂纹和剥落等失效形式和其产生原因。论证了氨氮氮化和离子氮化工艺可避免裂纹和剥落的产生。     

渗氮技术与渗氮钢应用综述

综述了包括气体渗氮、离子渗氮、洁净氮化、两段氮化和高频氮化等现有渗氮技术的应用现状,比较了它们的技术参数和优缺点。与渗碳相比较,简述了渗氮处理对零件表面强化的优点和实用性,并对渗氮钢的发展做了介绍。分析了各种合金元素和稀土元素对渗氮钢渗氮性能的影响。最后,展望了渗氮技术和渗氮钢的开发。     

外加热式离子氮化高速钢的研究

用外加热方式在管状反应室中对高速钢试样进行离子氮化，对氮化层的厚度变化、表面硬度及冲击韧性随Ｈ２／Ｎ２、渗氮温度及时间的变化进行研究。并且对普通离子渗氮试样与外加热离子渗氮试样进行比较     

TC4表面激光渗氮研究

以TC4合金为基材,利用连续激光器对表面激光渗氮,生成了金黄色的氮化层。用SEM,EDS,XRD对试样渗氮层的微观组织结构、元素分布以及物质组成进行了分析,结果表明生成了氮化钛的缺位式固溶体。表层由氮化层、热影响区及母材组成。渗氮层与基材之间处于完全冶金结合状态,结合力大,不易剥落。利用显微硬度仪对渗氮层进行硬度分析,表层硬度提高了4倍以上,显微硬度≥1000HV0.3的厚度超过100μm。     

纯铁及结构钢快速气体渗氮工艺及机理研究

研究了纯铁及38CrMoAlA钢分别在500℃、0~0.4MPa压力和510℃、0~0.5MPa压力条件下的氨气渗氮行为。提高渗氮压力可显著加速气体渗氮动力学过程,纯铁在500℃和0.4 MPa下气体渗氮处理5h后渗氮层厚度(1160μm)可同比达到常规渗氮层厚度(205μm)的5倍以上,而38CrMoAlA钢经510℃和0.5 MPa压力下渗氮5h后的渗氮层厚度(400μm)几乎与常规渗氮50h所得硬化层厚度(440μm)相当。同时,纯铁及38CrMoAlA钢渗氮层中ε-Fe2-3N与γ′-Fe4N的相比例、氮势及表层硬度均随压力的提高呈现先增加后降低的变化趋势。提出了一种合金结构钢表面高强高韧渗氮层快速复合制备工艺(增压渗氮+冷轧)。与一段式常规渗氮及增压渗氮工艺相比,复合工艺处理表层硬度及韧性均较优良,尤其高剪切应力磨损条件下复合处理表层的耐磨性能最优,在20~600℃热循环处理10~300次条件下复合处理表层的耐热疲劳性能最佳。研究了42CrMo钢在既定的渗氮周期内(6h)以NH3为介质,530℃及不同压力循环次数条件下的气体渗氮行为。在渗氮温度和总时间相同条件下,循环压力气体渗氮样品化合物层随压力循环次数的增加逐渐减薄,渗氮层整体厚度随压力循环次数的增加逐渐增加,同时渗氮表层韧性随压力循环次数的增加逐渐增强。     

Normal and anormal microstructure of plasma nitrided Fe-Cr alloys

Plasma nitriding behavior of Fe-Cr alloys has been studied at temperatures in the range of 773–873 K in order to provide basic knowledge for microstructure design of nitrided layers and to improve the wear resistance. In the nitriding temperature of 773 K, typical microstructure of nitrided layers was observed as reported elsewhere. However, anormal microstructure of nitrided layers was observed under a nitriding condition, at 873 K for 176.4 ks (49 h). In Fe-13Cr alloy, nitrided layer showed stripe-pattern, each sub-layer of which has different chromium content. Nitrided layer hardness increased gradually from the specimen surface to the nitriding front before dropping drastically to the same level as matrix hardness. The stripe-pattern was also observed for Fe-3Cr alloy at the vicinity of nitriding front for the same nitriding conditions. On the other hand, nitrided layers in Fe-8Cr and Fe-19Cr alloys are composed from different sub-layers, containing different concentration of chromium. These phenomena cannot be explained only by nitrogen diffusion process during the nitriding.     

Microstructure and Tribological Properties of Plasma Nitriding Cast CoCrMo Alloy

A medical cast CoCrMo alloy was coated by plasma nitriding process to enhance the wear resistance.The microstructures,phases and micro-hardness of nitrided layers were investigated by atomic force microscopy(AFM),scanning electron microscopy(SEM),X-ray diffraction(XRD) and micro-hardness.Tribological properties were investigated on a pin-on-disc wear tester under 25% bovine serum solutions.The experimental results showed that plasma nitriding was a promising process to produce thick,hard and wear resistant layers on the surface of CoCrMo alloy.The harder CrN and Cr2N phases formed on the plasma nitrided layer with the compact nano-crystalline structure.Compared with the untreated sample,all nitrided samples showed the lower wear rates and higher wear resistance at different applied loads and nitriding temperatures.It was concluded that the improvement of wear resistance could be ascribed to the formation of thicker and harder nitrided layers with the specific microstructures on nitrided surfaces.     

Analysis of Gas Nitriding Characteristics Under Different Cold Hardening and Nitriding Pressure Conditions for Low-Carbon Low-Alloy Steel

Strength of Materials - A new approach to quick preparation of a nitrided case for low-carbon low-alloy steels was proposed. It is based on cold hardening and pressurized gas nitriding. The...     

Effects of DC plasma nitriding parameters on microstructure and properties of 304L stainless steel

A wear-resistant nitrided layer was formed on a 304L austenitic stainless steel substrate by DC plasma nitriding. Effects of DC plasma nitriding parameters on the structural phases, micro-hardness and dry-sliding wear behavior of the nitrided layer were investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, micro-hardness testing and ring-on-block wear testing. The results show that the highest surface hardness over a case depth of about 10 µm is obtained after nitriding at 460 °C. XRD indicated a single expanded austenite phase and a single CrN nitride phase were formed at 350 °C and 480 °C, respectively. In addition, the S-phase layers formed on the samples provided the best dry-sliding wear resistance under the ring-on-block contact configuration test.     

Kinetics and wear behaviour of M50NiL steel plasma nitrided at low temperature

The quenched M50NiL steel was plasma nitrided at 460°C for different time to investigate the effects of the duration time on the microstructure, microhardness and wear resistance of the nitrided layers. The results show that the plasma nitrided layer depth increases with increasing nitriding time. The plasma nitrided layer includes only the diffusion layer without compound layer. The main phases in the nitrided surface layer are nitrogen expended α′-Fe and γ′-Fe₄N. The microstructure of the nitrided layer is refined. The wear resistance of the nitrided samples can be improved significantly by plasma nitriding. The sample nitrided for 4?h possesses the highest wear resistance, due to its relatively smooth surface and ultra-fine grains in the nitrided layer.     

Anwendungsmöglichkeiten des Pulvernitrierens im Vergleich zum Badnitrieren (Tenifer-Verfahren)

Application of powder nitriding in relation to bath nitriding (Tenifer-process) Powder nitriding depends on thermal decomposition of lime nitrogen. This process is very simple, opposite to bath nitriding not requiring any expensive equipment. Only small specimens should be nitrided by this method. In relation to bath nitriding of 90 minutes powder nitriding should last nearly five hours. As after bath nitriding a zone of nitrides and a zone of diffusion formed on the surface of specimens. No pores were visible in the zone of nitrides of powder nitrided specimens.     

金属钛激光气体氮化层组织及表面特征

采用连续波Nd-YAG激光在氮气环境中对金属钛进行激光气体氮化处理.利用SEM,XRD,XPS研究氮化层的显微组织、表面成分、结构.结果表明:通过激光气体氮化可以在金属钛表面得到表面相对平滑、无裂纹的氮化层;氮化层与基体材料之间为冶金结合.氮化层主要由枝晶状TiN组成,同时有TiNxOy,TiO2及TiC存在,外表面有C,O污染或吸附;TiN枝晶密度由表面沿深度方向下降.     

不同温度下等离子渗氮后TC4钛合金的摩擦磨损性能EI北大核心CSCD

采用等离子渗氮技术提升TC4钛合金的耐磨性并探究最优渗氮温度。利用LDM 1-100型等离子渗氮设备,在650,700,750,800,850℃和900℃温度下对TC4钛合金进行渗氮处理,保温时间均为10 h。利用光学显微镜、扫描电子显微镜、白光三维形貌仪、X射线衍射仪和显微硬度计分别对不同温度渗氮试样的微观组织结构、表面形貌、表面粗糙度、相结构和硬度进行表征。利用CETR UMT-3型多功能摩擦磨损试验机测试等离子渗氮后TC4钛合金的摩擦学性能。结果表明:TC4钛合金表面显微硬度和粗糙度随温度升高而增大,在900℃渗氮后TC4钛合金表面显微硬度达到了1318HV 0.05,约为基体(360HV 0.05)的4倍。硬度的升高是由于渗氮后试样表面形成了硬质氮化物相(TiN和Ti2N相),且随着渗氮温度升高氮化物的含量增加。相较于低温渗氮(低于750℃)的试样,850℃和900℃渗氮试样的承载能力显著提升。与原始TC4试样相比,渗氮处理后试样的磨损体积显著降低。当渗氮温度为850℃时,试样磨损体积为未处理试样磨损体积的1.2%(1 N),3.0%(3 N)和62.2%(5 N),试样的耐磨性提升更为显著。