回火工艺对H13模具钢渗氮层的影响

用光学显微镜、扫描电镜及X射线衍射仪等研究了淬火+不同回火工艺处理H13模具钢再经相同气体渗氮处理后的渗层组织,用显微硬度计测试了渗层横截面的硬度,分析了回火工艺对渗氮层的影响.结果表明:经淬火+两次350℃回火的试样再渗氮后渗层较致密,硬度变化较平缓,但渗层厚度低于淬火+两次600℃回火后渗氮试样的;淬火+两次600...     

氮气-甲烷离子氮碳共渗工艺的研究

利用金相显微镜、扫描电镜和X射线衍射仪对经氮气-甲烷离子氮碳共渗的40Cr钢进行了分析,并测定了渗层中沿层深方向的显微硬度分布.结果表明渗层可分为3层,即化合物层、扩散层和基体组织.表面渗层物相结构主要由氮(碳)ε化合物和Fe3C构成;在适当的工艺条件下,可以获得表层硬度高达525 HV(0.1),沿层深方向硬度分布合理、脆性低的渗层;与常规离子渗氮相比,以氮气-甲烷混合气体作为气源的离子氮碳共渗工艺成本低廉,绿色环保.     

TC4钛合金表面低压渗氮层的显微组织与耐磨性能

为了提高TC4钛合金的表面硬度及耐磨性,对其进行了820℃×10h的低压渗氮处理;通过X射线衍射仪、光学显微镜、扫描电子显微镜、显微硬度计及磨损试验机研究了表面渗氮层的显微组织与耐磨性能。结果表明:渗氮处理后,该钛合金表面形成了由表面氮化物层和次表面氮扩散层组成的渗氮层,其物相组成为TiN、Ti_2AlN和Ti_3Al;渗氮层的表面硬度为800~900HV,比基体的提高了近3倍,截面硬度随着深度的增加而下降;在相同条件下,渗氮后试样的磨损质量损失比未经渗氮处理的小,且随载荷的增加磨损质量损失增加更缓慢,耐磨性得到了极大的改善。     

钢的原始组织、渗氮层深度与显示方法的研究

渗氮处理是提高表面硬度、耐磨性、抗蚀性和疲劳强度的一种热处理方法。但是,在渗氮工艺参数给定的情况下,钢的原始组织对渗氮层的深度有较大的影响工件渗氮后渗氮层深度的测定一般都按照《GB11354-89钢铁零件、渗氮层深度测定和金相组织检验》进行测定,但在实际应用上,也有不便之处,本文主要以38CrMoAl和42CrMo钢为例进行了研究。     

H13钢表面不含白亮层的渗氮层制备及其耐磨性能

采用等离子氮化技术对H13钢进行离子氮化,通过改变渗氮气压和温度得到不同成分和厚度的渗氮层,用光学显微镜和X射线衍射仪分析了渗层的组织及物相组成,借助球-盘磨损试验机对渗层在大气环境下与Al_2O_3球对磨时的摩擦学性能进行了研究。结果表明:渗层主要由ε-Fe_(2-3)N、γ′-Fe_4N和少量α-Fe、Fe_2O_3、Fe_3O_4相构成;渗氮温度为510℃时没有形成明显的渗层,渗氮温度为570℃、气压为200,300 Pa和渗氮温度为540℃、气压为100 Pa时渗层只有扩散层,而在其他条件下渗层由白亮层和扩散层组成;氮化后表面硬度为1100～1200 HV,较基体增加1倍左右;在温度为570℃、气压200 Pa制备渗层的摩擦因数比基体大幅度降低,磨痕宽度变窄,比磨损率明显降低,耐磨性明显改善。     

离子硫氮复合渗42CrMo钢的耐磨性和抗咬合性研究

研究了离子硫氮复合渗对42CrMo钢的耐磨性和抗咬合性的影响。数据表明，与42CrMo钢调质态和单一离子渗氮工艺状态相比，该钢经离子硫氮复合渗处理后可明显提高钢的耐磨性和抗咬合性。通过对渗层的组织结构分析，探讨了硫氮复合渗层对提高42CrMo钢的耐磨性和抗咬合性的作用机理。     

光纤测温在离子渗氮炉中的应用

众所周知，离子渗氮具有渗速快、渗层组织易于控制、脆性和变形小、无公害等优点，经离子渗氮处理的零件，其表面硬度高，耐磨性好，且耐蚀性及疲劳强度都有较大的提高。然而，由于离子渗氮零件的热能获得与一般传统的加热方法不同，没有一个等温的炉膛，而是靠离子轰击自身发热的，     

4Cr5MoV1Si钢B—S复合渗最佳工艺

本文对4Cr5MoV1Si钢B—S复合渗的最佳工艺进行了探讨,从自配的多种固体粉末渗剂中筛选出最佳渗B配方,实现了有效渗硼;同时进行了低温液体渗S实验,筛选出最佳渗S配方。对B—S复合渗的渗层,用金相、显微硬度、磨损及X射线物相分析等技术进行了较系统的分析。实验结果表明:B—S复合渗可使耐磨性明显提高,同时改善了单纯渗B的表面硬度分布及脆性。     

G80Cr4Mo4V钢轴承套圈离子渗氮工艺优化试验

采用不同的离子渗氮工艺对G80Cr4Mo4V钢轴承套圈进行离子渗氮处理。采用金相显微镜、硬度计分析渗氮层组织、硬度以及渗氮层深度,借助X射线衍射仪对优化工艺处理的轴承套圈进行应力梯度对比分析。结果表明:降低溅射时间或延长脉冲停顿时间可以改善脉状组织级别;渗氮时间由30 h增至50 h后,渗氮层深度及硬度得到显著提高,继续增至75 h,渗氮层深度及硬度变化不再显著;氮氢比为1∶25,脉冲比为1∶6工艺条件下,G80Cr4Mo4V钢外圈在渗氮温度515℃、渗氮时间50 h、脉冲时间70μs、溅射时间3 h时性能最优。     

齿轮轴的离子渗氮处理

我厂承接了一批齿轮轴的离子渗氮处理件,零件外形尺寸见图1,材料为38CrMoAl。主要技术要求:渗氯层深度0.3～0.4mm,表面硬度700～7201TV(表面磨去渗氮层O.05mm后,硬度700～715HV),零件弯曲变形≤0.08mm。     

Laboratory assessment of wear on nitrided surfaces of dies for hot extrusion of aluminium

A newly designed “block-on-cylinder” wear resistance testing rig, which allows testing at higher contact pressures than conventional testing methods, was used to elucidate the effect of an iron nitride compound layer (white layer) on the wear resistance of nitrided dies used for hot extrusion of aluminium (Al). The tested dies (AISI H13) with various nitrided microstructures were provided by different manufacturers of equipment for plasma and gas nitriding. The wear surfaces were analysed by SEM, BEC, micrography and roughness measurements. It was found that the iron nitride compound layer is chemically more stable against hot Al in comparison to die material. Deterioration of the compound layer begins with cracking, and as a consequence, its spalling from the nitrided surface. A high thickness of the compound layer combined with a low nitriding depth leads to its earlier spalling and vice versa. Due to the increased roughness at the removal sites, accelerated chemical attack by hot Al takes place. Comparative and simultaneous testing of two nitrided samples was carried out.     

Several plasma diffusion processes for improving wear properties of Ti6Al4V alloy

Different kinds of diffusion processes, plasma nitriding, oxidizing and oxynitriding as of a combination of other two, have been applied to Ti6Al4V alloy to evaluate the effect of treatment times (1 and 4 h) and temperatures (650 and 750 °C) on wear properties of the alloy. It was observed that a hard modified layer was produced on the surface of the alloy after each diffusion process. While TiN and Ti₂N phases form in the modified layer with plasma nitriding, mainly TiO₂ phase forms after plasma oxidizing treatment. The wear tests performed at different normal loads showed that all treated samples, except for nitrided and oxidized at 650 °C for 1 h, exhibited higher wear resistance than untreated Ti6Al4V alloy. The plasma nitrided samples showed adhesive wear. On the other hand, while the plasma oxidizing samples displayed adhesive wear at lower loads, wear mechanism changed to abrasive wear as the load increased because the oxide film which covers the surface was broken during the sliding at higher loads.     

Multi-pass scratch test behavior of modified layer formed during plasma nitriding

316L stainless steel and Ti6Al4V alloy were plasma nitrided at different treatment parameters, and the wear behaviors of the modified layers formed on the surface during nitriding were investigated by multi-pass scratch test. Phase structure and cross-sections of modified layers were also examined with XRD and SEM. While a single modified layer formed on surface of the 316L stainless steel, both modified and diffusion layers were observed on the surface of the Ti6Al4V alloy after nitriding. As a result, it was observed that phase structure and thickness for modified layers of 316L stainless steel and Ti6Al4V alloy, respectively, were the significant parameters for friction coefficient and wear rate. In addition, diffusion layer formed during the nitriding process caused on increase of wear resistance of Ti6Al4V alloy by supporting the modified layer on the surface.     

Dry wear and friction behaviour of plasma nitrided Ti–6AL–4 V alloy after explosive shock treatment

The unlubricated wear behaviour of explosive shock treated and, subsequently plasma nitrided Ti–6Al–4 V alloy was studied using a ball-on-disc wear tester. Plasma nitriding was carried out at three different temperatures (700, 800 and 900 °C) for 3, 6, 9 and 12 h. Plasma nitriding after explosive shock treatment enabled a reduction in the wear rate of two orders of magnitude. Detailed investigations of this improved wear performance dependent on the nitriding temperature and time were carried out. The friction and wear data showed a clear breakthrough transition from the nitrided layer to the core of the Ti–6Al–4 V alloy matrix. The lowest wear volume was obtained for the sample, nitrided at 900 °C for 12 h, especially at loads of 2.5, 5 and 7.5 N. Obviously, the hard nitride layers were intimately associated with low wear rate, providing a smooth low friction surface. The coefficient of friction reduced from 0.46 to 0.2 due to a thick and hard compound layer resulting from a high nitrogen diffusion rate caused by explosive shock treatment that expected to increase point defects in the alloy. Detailed examination of the wear tracks showed that plasma nitriding changes the mechanism of wear from one of adhesion for untreated Ti–6Al–4 V to both delamination and mild abrasive.     

A comparative study on the tribological behaviors of nitrided and sulfur-nitrided 35CrMo steel lubricated in PAO base oil with MoDTC additive

A nitrided layer on 35CrMo steel was prepared by the ion nitriding process, and then a sulfur-nitrided layer was obtained by low temperature ion sulfuration. The results showed that both the nitrided and sulfur-nitrided surfaces improved the wear resistance efficiently under PAO lubrication, and exhibited the best wear resistance and friction-reducing property under PAO with 0.75% MoDTC lubrication. Compared with the plain and nitrided surfaces, the sulfur-nitrided surface exhibited the best synergistic effect with MoDTC displaying the lowest friction coefficient and wear volume. The mechanism of the best effect was due to MoS₂ and FeS formed on the sulfur-nitrided surface.     

Influence of plasma nitriding on fretting wear behaviour of Ti–6Al–4V

Plasma nitriding was performed on Ti–6Al–4V samples at 520 °C in two environments (pure nitrogen and a mixture of nitrogen and hydrogen in the ratio of 3:1) for two different time periods (4 and 18 h). Fretting wear tests were conducted on unnitrided and nitrided samples for 50,000 cycles using alumina ball counterbody. Plasma nitriding reduced the tangential force coefficient of Ti–6Al–4V. The samples nitrided for 4 h exhibited higher hardness and lower tangential force coefficient compared to the specimens nitrided for 18 h. The samples nitrided in nitrogen–hydrogen mixture environment exhibited higher hardness and lower tangential force coefficient compared to the specimens nitrided in pure nitrogen. The samples plasma nitrided in nitrogen–hydrogen mixture for 4 h exhibited the highest hardness and the lowest tangential force coefficient. The wear volume and specific wear rate of the plasma nitrided samples were lower than those of the unnitrided samples. A consistent trend was not observed regarding which nitriding condition would result in lower wear volume and specific wear rate at different loads.     

A comparative study on the tribological behaviors of nitrided and sulfur-nitrided 35CrMo steel lubricated in PAO base oil with MoDTC additive

A nitrided layer on 35CrMo steel was prepared by the ion nitriding process, and then a sulfur-nitrided layer was obtained by low temperature ion sulfuration. The results showed that both the nitrided and sulfur-nitrided surfaces improved the wear resistance efficiently under PAO lubrication, and exhibited the best wear resistance and friction-reducing property under PAO with 0.75% MoDTC lubrication. Compared with the plain and nitrided surfaces, the sulfur-nitrided surface exhibited the best synergistic effect with MoDTC displaying the lowest friction coefficient and wear volume. The mechanism of the best effect was due to MoS₂ and FeS formed on the sulfur-nitrided surface.     

Tribological behaviour of plasma nitrided Ti-5Al-2Nb-1Ta alloy against UHMWPE

A detailed study has been made on the wear behaviour of untreated and plasma nitrided Ti-5Al-2Nb-1Ta orthopaedic alloy against ultra high molecular weight polyethylene (UHMWPE) using pin on disc tribometer under lubricated conditions. The effects of nitriding temperature and nitriding time on the basis of the evolution of the wear volume loss and friction coefficient were investigated. The wear resistance of the plasma nitrided alloys increased considerably when compared to the untreated alloy. The wear debris identified using X-ray diffraction measurements indicated the formation of titanium oxide and titanium oxynitride particles. The wear rate was found to increase with increase in load and sliding velocity.     

渗氮GCr15钢在含氮硼酸酯添加剂润滑油作用下的摩擦学性能

针对提高滚动轴承使用寿命的问题,提出离子渗氮处理与添加剂结合的解决办法。用等离子渗氮炉在GCr15轴承钢表面制备了渗氮层,并用扫描电子显微镜(Scanning electron microscope, SEM )、X射线衍射仪(X-ray diffractometer, XRD)和显微硬度计观测了渗层的形貌、相结构和硬度变化。利用四球摩擦磨损试验机对比考察渗氮钢和未渗氮钢在含氮硼酸酯润滑条件下的摩擦学性能,并用X射线光电子能谱仪(X-ray photoelectron spectroscope, XPS)分析摩擦反应膜的成分与化学结合态。结果表明,渗氮层与润滑油添加剂之间发生了意想不到的良好交互作用,渗氮钢在质量分数为1.25%氮硼酸酯的润滑条件下表现出最低的摩擦因数和磨斑直径,比未渗氮钢分别降低了34%和45%;分析证明,渗氮层的摩擦表面生成了高BN质量分数的摩擦反应膜是获得优异摩擦学性能的主要原因,而在未渗氮钢摩擦表面未检测到BN。