Improvement of corrosion and wear resistances of AISI 420 martensitic stainless steel using plasma nitriding at low temperature

The influence of low temperature plasma nitriding on the wear and corrosion resistance of AISI 420 martensitic stainless steel was investigated. Plasma nitriding experiments were carried out with DC-pulsed plasma in 25% N₂ + 75% H₂ atmosphere at 350 °C, 450 °C and 550 °C for 15 h. The composition, microstructure and hardness of the nitrided samples were examined. The wear resistances of plasma nitrided samples were determined with a ball-on-disc wear tester. The corrosion behaviors of plasma nitrided AISI420 stainless steel were evaluated using anodic polarization tests and salt fog spray tests in the simulated industrial environment.The results show that plasma nitriding produces a relatively thick nitrided layer consisting of a compound layer and an adjacent nitrogen diffusion layer on the AISI 420 stainless steel surface. Plasma nitriding not only increases the surface hardness but also improves the wear resistance of the martensitic stainless steel. Furthermore, the anti-wear property of the steel nitrided at 350 °C is much more excellent than that at 550 °C. In addition, the corrosion resistance of AISI420 martensitic stainless steel is considerably improved by 350 °C low temperature plasma nitriding. The improved corrosion resistance is considered to be related to the combined effect of the solid solution of Cr and the high chemical stable phases of ?-Fe₃N and α_N formed on the martensitic stainless steel surface during 350 °C low temperature plasma nitriding. However, plasma nitriding carried out at 450 °C or 550 °C reduces the corrosion resistance of samples, because of the formation of CrN and leading to the depletion of Cr in the solid solution phase of the nitrided layer.     

The Study of Plasma Nitriding of AISI304 Stainless Steel

This paper presents results on the plasma nitriding of AISI 304 stainless steel at different temperatures in NH3gas. The working pressure was 100～200 Pa and the discharge voltage was 700～800V. The phase of nltrided layer formed on the surface was confirmed by X-ray diffraction. The hardness of the samples was measured by using a Vickers microhardness tester with the load of 50g. After nitriding at about 400℃ for two hours a nitrided layer consisting of single γN phase with thickness of 51.tm was obtained. Microhardness measurements showed significant increase in the hardness from 240 HV (for untreated samples) up to 950 HV (for nltrided samples at temperature of 420℃). The phase composition, the thickness, the microstructure and the surface topography of the nltrided layer as well as its properties depend essentially on the process parameters.     

304 不锈钢低温离子渗氮及氮碳共渗处理

目的研究304不锈钢离子渗氮层和氮碳共渗层的组织、硬度及耐磨、耐蚀性能,并考察渗层的磨损机理。方法利用离子渗氮及氮碳共渗工艺在304不锈钢表面获得硬化层,利用XRD,OM及共聚焦显微镜、显微硬度仪、电化学测试仪,分析处理前后渗层的组织、相结构及渗层的硬度及耐磨耐蚀性能。结果 304不锈钢氮碳共渗和渗氮层主要为S相层,在相同工艺条件下,氮碳共渗工艺获得的渗层为γN+γC的复合渗层,且厚度大于单一渗氮层。渗氮层和氮碳共渗层硬度约为基体硬度的3.5倍。在干滑动摩擦条件下,氮碳共渗层比渗氮层具有更好的耐磨性能;渗氮层的磨损机理为磨粒磨损的犁沟效应和断裂,氮碳共渗层的磨损机理为磨粒磨损的犁沟和微切削。电化学测试表明,渗氮层和氮碳共渗层的耐蚀性能均优于基体。结论 304不锈钢在420℃进行离子渗氮和氮碳共渗处理后,硬度和耐磨性能可大幅提高,且氮碳共渗处理效果更佳。     

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。     

Influence of plasma nitriding on plain fatigue and fretting fatigue behaviour of AISI 304 austenitic stainless steel

AISI 304 austenitic stainless steel samples were plasma nitrided at 420 °C for 6 h in vacuum atmosphere by glow discharge technique, in the presence of nitrogen gas. Plain fatigue and fretting fatigue tests were carried out on unnitrided and plasma nitrided samples. Plasma nitrided samples exhibited higher surface hardness, compressive residual stresses at the surface and lower surface roughness compared with unnitrided samples. However, plasma nitrided samples exhibited inferior plain fatigue and fretting fatigue lives compared with unnitrided samples. This was attributed to segregation of chromium at the grain boundaries of plasma nitrided specimens which might have weakened the regions near grain boundaries resulting in early crack initiation and accelerated crack propagation.     

Study of plasma nitriding and nitrocarburising of AISI 430F stainless steel for high hardness and corrosion resistance

ABSTRACT

In order to improve both the hardness and corrosion resistance properties of AISI 430F stainless steel, plasma nitriding (PN) and nitrocarburising processes were carried out at different temperatures ranging from 350 to 500°C for 4?h. After PN, the nitrided layer was found to be thicker compared to that obtained by plasma nitrocarburising process. There was an increase in microhardness values by a factor of six to seven compared to the plasma nitrided and nitrocarburised specimens respectively, treated at 500°C. The electrochemical corrosion behaviour of the plasma nitrided and nitrocarburised AISI 430F specimens show that the plasma nitrided and nitrocarburised specimens treated at 400°C for 4?h showed better corrosion resistance and higher surface hardness than the untreated AISI 430F stainless steel specimens. This is mainly attributed to the presence of nitrogen in the modified layer existing as a solid solution in the ferrite phase.

This paper is part of a supplementary issue from the 17th Asia-Pacific Corrosion Control Conference (APCCC-17).     

低温离子氮碳共渗温度对AerMet100钢摩擦学性能的影响

研究了不同温度对AerMet100钢渗氮层和氮碳共渗层的显微组织、表面硬度、渗层截面硬度梯度以及耐磨性的影响,并考察了渗层的磨损机理。结果表明,氮碳共渗层相较于渗氮层表面生成的化合物更加细小,表面更加平整光滑;离子渗氮、离子氮碳共渗处理都可显著提高AerMet100钢的表面硬度;随着温度的增加,共渗层厚度也明显增加;氮碳共渗层比渗氮层具有更低的摩擦因数,在共渗温度为480 ℃时氮碳共渗试样具有最低摩擦因数和磨损率,表现出最佳的耐磨性。渗氮层的磨损机理为氧化磨损和表面疲劳磨损,氮碳共渗层的磨损机理为氧化磨损、磨粒磨损以及表面疲劳磨损。     

液压柱塞泵用30CrMoV9钢的调质与气体渗氮工艺

为提高液压柱塞泵用30CrMoV9钢的综合性能及表面的耐磨性和抗疲劳性,对30CrMoV9钢的调质工艺及粗加工后的气体渗氮工艺进行了研究,对调质硬度、渗氮层深度、渗氮后的显微组织、渗氮层硬度等进行了测试。结果表明,经900 ℃淬火及630～640 ℃的回火处理后,30CrMoV9钢可满足硬度在28~35 HRC的要求;调质态30CrMoV9钢进行气体渗氮处理后,表面平均硬度可达750 HV0.5以上,可有效提高零件的接触疲劳强度。     

等离子渗氮与喷丸强化复合改进钛合金抗微动损伤性能

利用直流脉冲等离子电源装置对Ti6A14V钛合金表面渗氮处理,研究了渗氮层的相组成、硬度分布、韧度及摩擦学性能,采用喷丸形变强化(SP)对渗氮层进行后处理,以达到联合提高钛合金微动疲劳(FF)抗力的目的.研究结果表明:脉冲电源等离子技术可在钛合金表面获得由TiN、Ti2N、Ti2A1N等相组成的渗氮层,该改性层能够显著地提高钛合金常规磨损和微动磨损(FW)抗力,但降低了基材的FF抗力.渗氮层的减摩和抗磨性能与SP引入的表面残余压应力协同作用,使钛合金FF抗力超过了SP单独作用.提高渗氮层韧度对改善钛合金FF和FW性能均十分重要.     

Corrosion properties of plasma nitrided AISI 410 martensitic stainless steel in 3.5% NaCl and 1% HCl aqueous solutions

Samples of an AISI 410 martensitic stainless steel were plasma nitrided at a temperature of 420 °C, 460 °C or 500 °C for 20 h. The composition, microstructure and hardness of the nitrided samples were characterised using a variety of analytical techniques. In particular, the corrosion properties of the untreated and plasma nitrided samples were evaluated using anodic polarisation tests in 3.5% NaCl solution and immersion tests in 1% HCl acidic water solution. The results showed that plasma nitriding produced a relatively thick nitrided case consisting of a compound layer and a nitrogen diffusion layer on the 410 stainless steel surface. Plasma nitriding not only increased the surface hardness but also improved the corrosion resistance of the martensitic stainless steel. In the immersion test, nitrided samples showed lower weight loss and lower corrosion rate than untreated one. In the electrochemical corrosion tests, the nitrided samples showed higher corrosion potentials, higher pitting potentials and greatly reduced current densities. The improved corrosion resistance was believed to be related to the iron nitride compound layer formed on the martensitic stainless steel surface during plasma nitriding, which protected the underlying metal from corrosive attack under the testing conditions.     

The wear and corrosion properties of stainless steel nitrided by low-pressure plasma-arc source ion nitriding at low temperatures

Low pressure plasma arc discharge-assisted nitriding of AISI 304 austenitic stainless steel is a process that produces surface layers with useful properties such as a high surface hardness of approximately 1500 Hv_0.1 and a high resistance to frictional wear and corrosion. The phase composition, the thickness, the microstructure and the surface topography of the nitrided layer, as well as its properties, depend essentially on the process parameters. Among them, the processing temperature is the most important factor for forming a hard layer with good wear and corrosion resistance. Nitriding austenitic stainless steel at approximately 420°C for 70 min can produce a thin layer of 7–8 μm with very high hardness and good corrosion resistance on the surface. The microstructure was studied by optical microscopy and both glancing angle and conventional Bragg–Brentano (θ–2θ) symmetric geometry X-ray diffraction (XRD). The formation of expanded austenite was observed. Measurements of the wear depths indicated that the wear resistance of austenitic stainless steel can be improved greatly by nitriding at approximately 420°C using low-pressure plasma-arc source ion nitriding.     

稀土含量对Ti6Al4V钛合金等离子渗氮层组织和摩擦学性能的影响

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。     

38CrMoAlA、40Cr钢经不同渗氮工艺处理后的性能研究

研究了38CrMoAlA和40Cr钢经气体渗氮、气体氮碳共渗、离子渗氮处理后渗氮层的组织、硬度、摩擦磨损和腐蚀性能。试验结果表明，38CrMoAlA钢渗氮层的硬度及在3．5％NaCl溶液中的耐蚀性能高于40Cr钢，但抗摩擦磨损性能不如40Cr钢。依气体渗氮、气体氮碳共渗到离子渗氮的顺序，渗氮层的抗磨损性能逐次提高，但抗腐蚀能力逐次降低。从钢的化学成分、渗氮层的硬度和韧性出发，对38CrMoAlA和40Cr钢渗氮层的性能差异进行了分析与总结。     

钒对Cr12Mo模具钢渗氮层及其摩擦学行为的影响

在Cr12Mo和Cr12MoV模具钢表面进行气体渗氮处理,对比分析了V对Cr12Mo模具钢渗氮层显微结构及其摩擦学行为的影响。结果表明,气体渗氮后两种模具钢的表面均制备出深度约120 μm的渗氮层,由表及里依次为渗氮层、扩散层和基体;V提高了模具钢的耐磨性,Cr12MoV表现出较好的耐磨效果;相比V对模具钢基体和扩散层硬度的提升而言,V对渗氮层最大硬度值附近区域的硬度提升幅度更为明显;V对两种模具钢渗氮层耐磨性的影响并不明显,但V的主要贡献在于促进了渗氮时N的有效渗入,大大提高了渗氮层与扩散层间的界面结合力,避免了渗氮层与扩散层间的开裂,促使磨损机制由疲劳磨损转变为黏着磨损,进一步提高了渗氮层的服役寿命。     

The corrosion and corrosion-wear behaviour of plasma nitrided 17-4PH precipitation hardening stainless steel

Plasma surface nitriding of 17-4 PH martensitic precipitation hardening stainless steels was conducted at 350 °C, 420 °C and 500 °C for 10 h using a DC plasma nitriding unit, and the surface properties of the plasma surface engineered samples were systematically evaluated. Experimental results have shown that the surface properties of the plasma nitrided layers in terms of hardness, wear resistance, corrosion behaviour and corrosion-wear resistance are highly process condition dependent, and it is feasible to provide considerable improvement in wear, corrosion and corrosion-wear resistance of 17-4PH steel using optimised plasma treatment conditions. All three treatments can effectively improve the surface hardness and the sliding wear resistance under unlubricated conditions; high temperature (420 °C and 500 °C) treated materials revealed improved corrosion and corrosion-wear properties due to the formation of surface compound layers.     

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。     

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.     

Surface modification of austenitic stainless steel with plasma nitriding for biomedical applications

In the present study, plasma nitriding of AISI type 303 austenitic stainless steel (SS) specimens was performed using a microwave system. The nitrided layers were characterized by performing scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and a Vickers microhardness test. The antibacterial activities of the nitrided layers were evaluated. XRD and TEM showed that a single γ_N phase was formed by plasma nitriding at the plasma power of 700 W and 450 °C. The analytical results demonstrated that the hardness of type 303 specimens could be enhanced by plasma nitriding because of the formation of the γ_N phase. A bacterial test also demonstrated that the nitrided layer exhibited excellent antibacterial properties.     

预氧化+稀土铈对42CrMo钢离子渗氮的影响

针对离子渗氮渗层浅及生产周期长等技术难题,采用预氧化与稀土复合催渗对工程常用结构钢42CrMo进行了离子渗氮。利用显微硬度计、光学显微镜(OM)、扫描电镜(SEM)等对渗氮速率、渗氮层组织、表面形貌等进行了系统的研究。结果表明,经400 ℃×1 h氧化+0.6 cm²/kg(铈表面积/装炉量)稀土的复合催渗工艺具有最佳催渗效果;与无催渗试样相比,优化后的复合催渗不仅提高了渗氮效率,同时减少了脉状氮化物,且降低了渗氮层的硬度梯度。     

Wear Properties of Plasma Nitrided H13 Steel at Room and Elevated Temperature

H13 steel was nitrided using a plasma surface alloying technique at the temperature of 570℃.The nitrided layers with different thicknesses and components were obtained by changing nitriding pressure.The microstructure and composition of the nitrided layers were evaluated by optical microscopy(OM)and X-ray diffraction(XRD).The wear properties of the nitrided layer against Al2O3 ball at room temperature using a ball-on-disc tribometer and against Si3N4 ball at elevated temperature using a HT-2001 abrasive wear test machine were investigated.The results show that the nitrided layers are composed of compound layer and diffusion layer at the pressure of 100 and 450 Pa.No obvious compound layer appears at pressure of 200 and 300 Pa.XRD analysis shows the nitrided layers are mainly composed ofε-Fe2-3N,γ’-Fe4N,α-Fe,Fe2O3 and Fe3O4 phases.The surface hardness of plasma nitrided H13 steel is about 1100HV0.050 doubled that of substrate.The room temperature friction coefficient of H13 steel is reduced and wear rate is decreased by nitriding at 200 and 300 Pa.Elevated temperature wear test indicates the nitrided H13 steel at the pressure of 100 Pa shows lower friction coefficient and wear rate which are reduced more than 6 times compared with that of H13 substrate.