空气/甲烷混合气体离子氮化工艺研究

研究了一种利用空气/甲烷混合气体进行离子氮化的新工艺,分析了渗层的硬度、组织及物相.结果表明,通过加入甲烷气体,可以实现用空气直接进行离子氮化处理,通过调整甲烷流量,可以获得不同的渗氮硬度和物相.     

空气/乙炔混合气体离子氮化工艺研究

研究了一种利用空气/乙炔混合气体进行离子氮化的新工艺,并分析了渗层的硬度、组织及物相.结果表明,通过加入乙炔气体,可以实现用空气直接进行离子氮化处理,通过调整乙炔流量和渗氮温度,能实现离子多元共渗,并能获得一定的渗氮层深度和硬度.     

钛合金的氮化处理

本文对钛合金的硬氮化、离子氮化进行了初步探索。钛合金和钢铁一样,也可以进行氮化处理,其表层硬度可高达HV881.8,相当于HRC66。钛合金在铁基阴极的离子氮化过程中,在渗氮的同时,其表层的含铁量明显增加,并形成γ(Fe_4N)及ε(Fe_3N)相。     

离子能流密度对AISI304不锈钢氮化层摩擦性能的影响

采用低温等离子体氮化技术,对AISI304不锈钢进行表面氮化处理。考察了离子能流密度对不锈钢氮化层性能的影响。运用X射线衍射、扫描电镜和显微硬度计等分析手段对氮化层的物相组成及表面硬度进行分析及测量;利用球-盘摩擦实验在干摩擦条件下对氮化层的摩擦磨损性能进行测试。结果表明:AISI304不锈钢经低温等离子体氮化处理后,形成单一高氮面心立方相γN。在氮化处理过程中,离子能流密度受工作压力及基片负偏压影响较大。离子能流密度变化能显著影响不锈钢氮化层的摩擦性能,随着离子能流密度的增加,氮化层显微硬度增大,摩擦系数减小,耐磨损性能上升。     

辉光离子氮化对马氏体不锈钢性能的影响

对1Crl3马氏体不锈钢进行了辉光离子氮化处理试验,并对氮化试样的金相和硬度进行了分析测定.结果表明520℃辉光离子氮化8h,使1Crl3马氏体不锈钢的氮化层深度达到0.25mm,最高硬度达到HV732,约为基体硬度的4倍.     

离子氮化处理对涂层组织与耐磨性能的影响

研究了NiCrBSi自熔合金炉熔涂层的离子氮化后处理工艺，考察了离子氮化处理对涂层组织与耐磨性能的影响。结果表明，NiCrBSi合金涂层经离子氮化处理后，在其表面区（宽度约50μm）形成了弥散分布的尺寸小于5μm的颗粒状氮化物相（如CrN,BN等），表面硬度从800HV0.01提高到1300HV0.01左右，耐磨性能因此得以显著提高，从38CrMoAl氮化钢的20％－25％提高到优于氮化钢2－3倍。由于已存在高硬度WC颗粒相的强化作用，含20％WC的NiCrBSi昨合涂层的耐磨性能在离子氮化处理后没有明显改善。     

不同表面状态的32Cr2MoV的滑动摩擦试验比较

对复合镀膜处理的32Cr2MoV、离子氮化的32Cr2MoV和离子氮化后机械抛光的32Cr2MoV进行了滑动摩擦试验,并对比分析了三者的组织和显微硬度.结果表明,3种试样表面都呈现磨粒磨损的特征.在3种处理当中,复合镀膜的32Cr2MoV表面粗糙度比镀膜前高,但是表层0.2mm范围内镀膜后的显微硬度最高,摩擦力、摩擦系数、磨痕宽度、磨损量较离子氮化试样和离子氮化后抛光试样低,磨痕较浅,耐磨性最好.从观察结果还发现,离子氮化试样经过表面抛光后虽然表层硬度下降,但是其粗糙度远远低于抛光前,弥补了硬度下降对耐磨性的不利影响,使得其耐磨性有所提高.     

铪在钼合金离子氮化中的作用和影响

对Mo-Ti-Zr-C和Mo-Zr-Hf-C两种钼合金进行离子氮化处理。实验结果表明,含Hf钼合金在800℃离子氮化效果好,元素Hf能明显促进钼合金的离子氮化过程,增加了表面化合物层和硬化区的深度,提高了表面层硬度。     

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。     

40Cr钢离子氮化与离子镀TiN复合涂层与苜蓿草粉之间的摩擦学特性

在橡胶轮磨料磨损实验机上考察了40Cr钢基体上离子氮化与离子镀TiN复合涂层在苜蓿草粉软磨料下的摩擦学特性。采用划痕法测定了涂层的结合力,利用XRD分析了涂层的相结构,应用扫描电子显微镜观察分析了涂层磨损表面形貌和磨损机理。结果表明:离子氮化与离子镀TiN复合涂层的膜基结合力和硬度均高于TiN涂层;其对于苜蓿草粉软磨料的耐磨性也高于TiN涂层和渗氮层;离子氮化过渡层能显著提高TiN涂层的膜基结合力并改善薄膜的韧性;涂层能有效限制硬质颗粒对基体的压嵌和切削。涂层在苜蓿草粉软磨料下的磨损机制既包括硬质颗粒磨料条件下的切削磨损,也包括软磨料条件下的多次塑性变形和周期疲劳磨损。涂层硬度和韧性的共增可以提高其对软磨料的耐磨性。     

离子渗氮温度对W9Mo3Cr4V钢渗层组织及性能的影响

目前,国内外对搅拌头材料W9Mo3Cr4V钢离子渗氮表面改性研究不多。采用金相分析、显微硬度测量、X射线衍射仪(XRD)等研究了离子渗氮温度对W9Mo3Cr4V钢搅拌头显微组织和性能的影响,从而得出制备高硬度耐磨氮化层搅拌头的合适的离子渗氮温度。结果表明:经离子渗氮的W9Mo3Cr4V钢搅拌头表层获得了主要由ε相(Fe3N)和γ’相(Fe4N)组成的均匀渗氮层,且随着从表面到基体距离的增加,渗氮层的硬度呈现平缓的硬度梯度分布;480~560℃范围内,随离子渗氮温度升高,渗氮层厚度不断增加,渗氮层硬度也不断提高;ε相(Fe3N)衍射峰随离子渗氮温度升高而逐渐降低,γ’相(Fe_4N)衍射峰则呈逐渐升高的趋势。渗氮层厚度ζ与渗氮温度T的关系满足ζ=3.85×108e-9 141/T·τ。     

A Study on Formation and Growth Mechanism of Nitride Layers During Plasma Nitriding Process of Plastic Injection Mold Steel

Ion nitriding modifies composition of surface layer in steel used in plastic mold application and this consequently improves their lifecycle. In this study, pulsed plasma nitriding technique was used to produce a protecting hard layer on AISI P20 steel at three process temperatures of 450°C, 500°C, and 550°C for durations of 2.5, 5, 7.5, and 10 h at a constant gas mixture of 75% N₂–25% H₂. Surface morphology was studied by optical and scanning electron microscope and the phases formed on the surface layer were determined by X-ray diffraction (XRD). Elemental depth profile was measured by techniques including energy dispersive spectroscopy, wavelength dispersive spectrometer, and glow discharge spectroscopy and for identifying hardness profile, microhardness variations from surface to core of samples were recorded. Results showed that, thickness of compound layer of plastic mold steel AISI P20 was negligible. Moreover in ion nitriding of AISI P20, nitride were formed and grown in some preferred directions and upward diffusion of carbon and downward diffusion of nitrogen occurred during ion nitriding of AISI P20. XRD results showed that, ?-nitride is the dominant phase after plasma nitriding in all strategies. Furthermore, ion nitriding improved hardness of AISI P20 up to three times and as time and temperature increased, hardness and hardness depth of diffusion zone increased considerably.     

表面纳米化预处理对316L不锈钢渗氮层摩擦学性能的影响

为改善奥氏体不锈钢的表面硬度和耐磨性,采用超声滚压与离子渗氮复合工艺对316L不锈钢表面进行了表面强化处理。利用扫描电镜(SEM)、硬度计、X射线衍射仪(XRD)和能谱仪以及摩擦磨损试验机等测定了渗氮层的硬度、深度、含氮量和物相组成,研究了表面晶层组织结构对离子渗氮行为和渗氮层在润滑油条件下摩擦学性能的影响。结果表明:直接渗氮和超声滚压/渗氮试样表层组织均由S、γ'、ε和Cr N相组成,渗氮层厚度均为20μm,直接渗氮层以S相为主,超声滚压后渗氮层以ε和γ'相为主,组织结构较为致密;超声滚压/渗氮层的平均渗氮含量是直接渗氮层的2.88倍,摩擦系数降低了0.04,显微硬度和耐磨性是直接渗氮层的1.15倍和2.76倍;超声滚压处理诱使316L不锈钢表面形成的纳米晶层组织结构增强了渗氮试样表面的催渗效能和对渗氮层的支撑强度,超声滚压后渗氮试样的表面耐磨性能最好。     

Investigation of the formation of Al,Fe, N intermetallic phases during Al pack cementation followed by plasma nitriding on plain carbon steel

Plain carbon steels are not suitable for nitriding as they form an extremely brittle case that spalls off readily, and the hardness increment of the diffusion zone is small. In this research, the effect of plasma nitriding time and temperature variation on the microstructure of the pack cemented aluminized plain carbon steel is investigated. All samples were aluminized at 900 °C for 2 h; the aluminized samples were subsequently plasma nitrided at 500 °C, 550 °C and 600 °C for 2.5, 5, 7.5 and 10 h. The phases formed on the sample surface were detected by X-ray diffraction (XRD). The cross section and samples surface were investigated by optical and scanning electron microscopy (SEM). Microhardness test was conducted to determine hardness change from the surface to the sample core. Results showed that by aluminizing the steel, Fe₃Al phases as well as Fe–Al solid solution were formed on the surface and some aluminum rich precipitates were formed in solid solution grain boundaries. Plasma nitriding of the aluminized layer caused the formation of aluminum and iron nitride (AlN, Fe₄N) on the sample surface. Consequently, surface hardness was improved up to about eight times. By increasing the nitriding temperature and time, aluminum-rich precipitates dissociated. Moreover, due to the diffusion of nitrogen through aluminized region during ion nitriding, iron and aluminum nitrides were formed in aluminized grain boundaries. Increasing nitriding time and temperature lead to the growth of these nitrides in the grain boundaries of the substrate. This phenomenon results in the increment of sample hardness depth. Plasma nitriding of aluminized sample in low pressure chamber with nitrogen and hydrogen gas mixture reduced surface aluminum oxides which were formed in aluminizing stage.     

Effects of various nitriding parameters on active screen plasma nitriding behavior of a low-alloy steel

Active screen plasma nitriding (ASPN) is a novel surface modification technique that has many capabilities over the conventional DC plasma nitriding (CPN). In this study, 30CrNiMo8 low-alloy steel was active screen plasma-nitrided under various nitriding parameters such as active screen set-up parameters (different screen hole sizes, mesh sheet and plate top lids) and treatment temperature (520, 550 and 580 °C), in the gas mixture of 75% N₂+25% H₂ and chamber pressure of 500 Pa for 5 h. The properties of the nitrided specimens have been assessed by evaluating composition of phases, surface hardness, compound layer thickness and case depth using X-ray diffraction (XRD), microhardness measurements and scanning electron microscopy (SEM). It was found that the screen hole size and top lid type (mesh or plate) play an important role in transition of active species (nitrogen ions and neutrals) toward the sample surface, which in turn can affect the nitrided layer hardness and thickness. Treatment at higher temperature with bigger screen hole size resulted in a thicker compound layer and higher layer hardness. The compound layers developed on the samples treated under different conditions were dual phase consisting of γ′-Fe₄N and ε-Fe_2-3N phases.     

Saddle field fast atom beam source: A new low pressure plasma nitriding method for a alloy Ti-6Al-4V

Ti and its alloys (Ti-6Al-4V) have been used in different engineering applications due to their several outstanding properties. Nevertheless, their use in practical applications is limited in many cases due to their poor tribological property. Researches are ongoing on surface modification of Ti based materials by different plasma and ion based techniques to overcome this problem. However, the conventional plasma nitriding techniques have several problems such as formation of an arc, increased possibility of surface contamination due to a comparatively higher operating pressure, production of a very thin nitrided layer after a long processing time, etc. In this present work, the possibility of a new low-pressure plasma nitriding process using a Plasma Enhanced Chemical Vapor Deposition (PECVD) based saddle field fast atom beam source on a Ti-6Al-4V alloy sample is investigated. Plasma nitriding was carried out at 900 °C and at a pressure 0.1 Pa for 8 h by using a beam current 0.5 A. Optical Microscopy investigation of the cross-section of the nitrided sample revealed a compound nitrided layer (thickness approximately 16 μm) followed by a diffusion layer. X-Ray Diffraction (XRD) analysis confirmed the presence of a TiN phase in the nitrided layers. A roughly three fold higher hardness value (1578 HV_0.015) in the top nitriding layer was observed by Vickers microhardness testing compared to hardness value of untreated sample (568 HV_0.015),with a gradually decreasing hardness in the core material. The results show that this is a promising method for low pressure plasma nitriding of Ti alloy within a short processing time compared to the conventional nitriding process.     

Influence of Ultrafine‐Grained Layer on Gaseous Nitriding of Large‐Sized Titanium Plate

In this paper, mechanical shot blasting on a large sized titanium plate is conducted to induce severe plastic deformation, which generates an ultrafine‐grained surface layer. The effect of an ultrafine‐grained layer on nitriding is evaluated at nitriding temperatures from 600 to 850 °C. The structural phases and mechanical property improvements are investigated and compared to those of a coarse‐grained specimen by using X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and mechanical property measurements. The results indicate that an ultrafine‐grained layer enhances the nitriding kinetics and produces a thicker nitrided layer than that of a coarse‐grained plate at the same gaseous nitriding temperatures. The improved kinetics are attributed to a greater number of grain boundaries and defects introduced into the titanium plate surface by the mechanical shot blasting treatment. Meanwhile, the surface and cross‐sectional hardness values improve compared to the coarse‐grained plate due to the thicker nitrided layer resulting from deeper nitrogen diffusion.     

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.     

Hydrogen-free nitriding of ZrTiAlV by double glow plasma discharge improving the wear resistance

A hydrogen-free nitriding method through double glow plasma metallurgy is exploited and a nitrided layer was formed on ZrTiAlV alloy. The nitrided layer was characterised through X-ray diffraction, optical microscopy, scanning electron microscopy and energy-dispersive spectroscopy techniques, as well as through Vickers hardness and friction and wear tests. Results showed that the nitrided layer is 580?µm thick, homogeneous and dense. It mainly consists of TiN, Ti₂N and ZrN phases. The hardness of the nitrided layer on the surface of the ZrTiAlV alloy is nearly 2.5 times higher than that of the ZrTiAlV substrate. The friction coefficient and wear resistance of the alloy considerably improved after nitriding.     

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.