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钽等离子体渗氮的表面过程分析 总被引:9,自引:1,他引:8
对钽表面渗氮的固-气界面反应过程进行了热力学和动力学分析,从到理论预测了各种参数(压力、气体、组成、温度、电参数等)对表面过程的影响,并借助于等离子体,在较你廿获得由层与N在TA中的固溶体组成的表面硬化层,层为六方晶系的Ta6N2,57和/或非昌态。通过调整工艺参数有效地抑制了钽表面氧的渗入和Ta2O5的形成,使得离子渗氮后,仍保持较低的表面粗糙度。 相似文献
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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。 相似文献
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The nitriding behavior of AISI M2 steel was studied on samples previously submitted to two different heat treatments in order to investigate the effects of the initial microstructure on the thickness and hardness of nitrided layer. Prior to nitriding, one group of samples was fully annealed while the other group was quenched and tempered, thus acquiring the lowest and highest hardness respectively. Plasma nitriding was performed at 450 °C for 8 h with a mixture of N2 and H2 in a plasma reactor working under floating potential. Structural and mechanical properties of nitrided layers were characterized using X-ray diffraction (XRD), optical microscopy and microhardness testing. Variations in surface roughness were obtained by 3D surface profilometry analysis. The thicker nitrided layer was obtained for the fully annealed samples, in which the nitrided layer is composed of γ′-Fe4N and ε-Fe2-3N phases plus a diffusion zone. For the hardened-tempered samples, the nitrided region mainly consisted of a diffusion zone. Plasma nitriding increased the surface hardness of the fully annealed samples by 330% and that of the quenched-tempered samples by 50%. The nitrided depth was also estimated using cross-sectional microhardness profiles; giving about 140 µm and ∼ 70 µm for the fully annealed and quenched-tempered samples, respectively. Due to the grain to grain nitrogen diffusion, plasma nitriding also increased the surface roughness. The largest roughness was obtained for the fully annealed samples, in accordance with the largest nitrided depth. The difference in the nitriding behavior was explained on the basis of the microstructural aspects of the substrates such as the concentration of the freely dispersed alloying elements and the level of compressive residual stresses. 相似文献
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对PH13-8Mo钢离子渗氮工艺参数进行了研究,其中包括渗氮温度、渗氮时间及渗氮件表面粗糙度。结果表明:随渗氮温度的升高、渗氮时间的延长、零件表面粗糙度的降低,PH13-8Mo钢渗氮层厚度增加;渗氮零件表面粗糙度对渗氮层脆性等级影响较大,渗氮零件表面粗糙度为6.3 μm时,其脆性等级达到III级;渗氮时间、渗氮温度及零件表面粗糙度对渗氮层硬度影响甚微。渗氮温度540 ℃,渗氮时间22 h,零件表面粗糙度0.8 μm时,PH13-8Mo钢可获得良好的渗氮层,渗氮层厚度可达197.5 μm,渗氮层硬度可达1083 HV0.2,脆性等级为II级。 相似文献
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目的研究稀土含量对Ti6Al4V钛合金表面等离子体渗氮层结构和性能的影响。方法运用等离子表面改性技术对Ti6Al4V(TC4)钛合金进行等离子渗氮处理,渗氮过程中通入不同含量的稀土作为催渗剂,以获得钛合金表面强化层。利用金相显微镜和扫描电子显微镜(SEM)观察渗氮层组织,用X射线衍射仪(XRD)分析渗层相组成,用能谱仪(EDS)检测渗层的化学成分,用维氏显微硬度计测量渗层的显微硬度,用球-盘式摩擦磨损试验机和三维轮廓仪检测渗层的摩擦磨损性能。结果TC4钛合金表面等离子渗氮层结构包括表面化合物层(主要成分为δ-TiN)和扩散层(主要为N原子扩散形成的N-Ti固溶体),加入稀土可以促进N原子向基体的扩散,提高渗氮速度。渗层厚度增加,硬度和耐磨性能提高,扩散层使钛合金基体与化合物层之间的硬度梯度更加平缓。当稀土通入速率为60 mL/min时,渗层厚度可达155μm,表面硬度为1275HV0.05,摩擦系数降到0.27,磨损率明显降低。结论钛合金等离子渗氮过程中加入稀土可以有效提高渗速,改善渗氮层硬度,提高材料表面的耐磨性能。 相似文献
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CoCr alloys are widely used for medical applications, e.g. total hip replacements or coronary stents. Nevertheless, an increase in the surface hardness and a reduction of the wear rate is still desirable to improve the biocompatibility. Plasma immersion ion implantation (PIII) at different temperatures, acceleration voltages and working pressures is used to determine the nitrogen diffusivity in the CoCr alloys SY21med, L605 and HS188. Depending on the temperature, two different treatment regimes can be distinguished, independent of the ion energy. At low temperatures, a diffusion process with an activation energy of 1.0-1.1 eV is present, indicative of interstitial nitrogen diffusion. Beyond 350 °C, a reduced activation energy of 0.5-0.7 eV is observed. Additionally, a strong dependency of the layer thickness on the working pressure in the range 0.3-0.8 Pa was observed for the temperature dependent diffusion regime, which suggests a synergistic interplay of adsorption and implantation during PIII. Below 500 °C, an increase of the diffusion coefficient by three orders of magnitude was observed for PIII, compared with pure plasma nitriding. 相似文献
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Duplex treatments by thermo reactive diffusion (TRD) chromizing and puls plasma nitriding were carried out on AISI 52100 and 8620 bearing steels. Tribological behaviors of TRD chromized and duplex treated bearing steels were investigated against Al2O3 ball in ball-on-disc system at room temperature and 500 °C. The samples were pack chromized in a furnace at temperature of 1000 °C for 5 h. After chromizing, the samples were puls plasma nitrided for 5 h at 500 °C. The coated steels were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), scratch and microhardness testing. Plasma nitriding of chromized steels increased the total thickness of the compound layer. The subsequent plasma nitriding increased the surface hardness to 2135 HK0.025 due to the formation of CrN and Cr2N. The surface hardness and scratch resistance of coating can be increased with duplex treatment of chromizing followed by plasma nitriding, resulting in high wear resistance. Tribological tests indicated that puls plasma nitriding process decreased the coefficient of friction values and wear rate of the chromized steels at room temperature and 500 °C. Also, examination of the worn surface of the samples showed that particularly at high temperature, the oxidized compact layer occurs and tribo-oxidation played an important role in oxidation behaviour of the steels after the duplex treatment. 相似文献
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O. Salas J. Oseguera N. García U. Figueroa 《Journal of Materials Engineering and Performance》2001,10(6):649-655
The performance of a dual plasma reactor in nitriding a H13 steel was investigated and compared to other nitriding methods
applied to this material. The aim was to explore the advantages of combining a weakly ionized plasma unit and a postdischarge
plasma reactor to process this material. Samples of H13 were nitrided at 500, 550, and 600 °C for times ranging between 5
to 10 h. The hardness distributions obtained revealed a substantial advantage of the present method over conventional gas
nitriding and some improvement over other plasma-assisted methods, especially in the development of smooth profiles. This
was attributed mainly to enhanced diffusion provided by the postdischarge flow. The evolution of hardness as a function of
time and temperature displayed an aging type of behavior that was related to the formation and growth of CrN as the hardening
phase. 相似文献
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采用OM、SEM、硬度测试、摩擦磨损试验等方法研究了QPQ技术中渗氮时间对合金铸铁组织与摩擦性能的影响。结果表明,QPQ处理后,合金铸铁表面形成的渗层物相主要由Fe2-3N、Fe2O3和FeO组成。渗层厚度的平方与渗氮时间存在线性关系,在580 ℃渗氮盐浴条件下,氮元素在合金铸铁中的扩散激活能为70.07 kJ/mol。在90~150 min渗氮时间内,随着渗氮时间延长,渗层的表面硬度值由522 HV0.05降低至441 HV0.05,当渗氮时间延长至180 min,表面硬度值回升至455 HV0.05。与未处理试样相比,QPQ处理的试样具有更小的摩擦因数,并且QPQ处理后试样表面的犁沟显著变浅,表面的金属剥落也得到明显改善,且随着渗氮时间的增加,渗层厚度增加且稳定材料。经180 min渗氮处理的QPQ试样具有最优综合性能,表面硬度值为455 HV0.05,摩擦因数为0.32。 相似文献
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H. Kuwahara H. Matsuoka J. Takada S. Kikuchi Y. Tomii I. Tamura 《Oxidation of Metals》1991,36(1-2):143-156
To clarify the mechanism of plasma nitriding, we examined the optical microstructure, the hardness, the precipitation, and the concentration of dissolved nitrogen in Fe-18Cr-9Ni nitrided using plasma in the range of 723–823 K. Compared with ammonia-gas nitriding, the features of plasma nitriding are the formation of small chromium-nitride precipitates (CrN), the absence of an externally nitrided layer, the high concentration of dissolved nitrogen, and the high hardness (HV=1200). The diffusion coefficient of nitrogen in the present alloy was determined using the growth rate of the internally nitrided layer, based on calculations used in internal oxidation. Plasma- and gas-nitriding were also compared with respect to the growth rate of the nitrided layer. 相似文献
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《International Heat Treatment & Surface Engineering》2013,7(4):139-143
AbstractA 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. 相似文献
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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. 相似文献
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研究了X80管线钢在3.5%NaCl溶液中的电化学腐蚀行为。结果表明:经离子渗氮的样品,表面硬度显著提高,且随渗氮温度的升高而增加;渗氮层的耐蚀性明显优于基体材料,腐蚀电流密度降低一个数量级;腐蚀电位明显正移。当渗氮温度为450 ℃时,样品渗氮层由ε相和少量的γ '相构成,表面硬度约为810 HV,耐蚀性最好,腐蚀电流最小,约为0.56 μA/cm2,腐蚀电位最高,约为-214 mV。当渗氮温度为570 ℃时,样品渗氮层全部为γ '相,表面硬度约为930 HV,耐蚀性明显降低。离子渗氮温度显著影响X80钢表面渗氮层的相组成,引起表面硬度和耐蚀性不同。 相似文献
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不锈钢低温渗氮/渗碳S相渗层技术的研究进展 总被引:2,自引:0,他引:2
奥氏体不锈钢通过低温渗氮/渗碳,获得含氮/碳固溶饱和的扩散层,即S相渗层,不仅提高了不锈钢表面硬度,而且还提高了不锈钢的耐蚀性。本文综述了不锈钢S相渗层研究与应用技术的最新研究进展,分析了低温离子渗氮/渗碳、气体低温渗氮/渗碳、高温渗氮固溶淬火及离子注入渗氮技术的工艺特点。讨论了S相渗层的力学性能和耐蚀性能,分析了国内S相低温渗层技术工业应用存在的问题,展望了S相技术的发展前景。 相似文献
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对表面残存不同厚度脱碳层的38CrMoAl钢塔形试样进行离子渗氮,借助显微硬度计、光学显微镜、扫描电镜等多种手段,对试样渗速、硬度及渗氮前后的微观组织进行研究。结果表明,在残余的脱碳层里存在较严重的魏氏组织;残余脱碳越严重魏氏组织越多;离子渗氮的渗速随着表面脱碳层厚度的增加先增加后降低;魏氏组织中大量的铁素体为氮原子扩散提供了快速渗入通道及形成大量氮化物的场所,在渗层表面形成大量的鱼骨状、网状、脉状氮化物,数量随着脱碳层的增加而增加,并且不断向渗层深处延伸。38CrMoAl钢表面残存脱碳层虽然有加快渗速的作用,但会增加渗层的不良组织,增加渗层剥落的风险。故38CrMoAl钢制工件做普通调质应适当加大加工余量。 相似文献