铝合金气缸内表面摩擦涂覆处理工艺的研究

为了提高铝合金气缸的表面硬度及耐磨性能,改善其高温性能,本文利用涂覆材料经过摩擦作用发生塑化和塑性流动后形成改质层的原理,对铝合金气缸内表面的摩擦涂覆工艺进行了研究。研究结果表明,在铝合金气缸内表面采用Al-Si13%合金和Al-Cu35%合金作为改质材料经过摩擦涂覆处理后,可形成比较稳定的硬质膜,涂覆层的细化更加均匀,结合界面和气缸内表面的形状都非常圆滑,改善了气缸的耐磨性,有利于发动机的小型轻量化。     

SLM成形表面织构对TC4钛合金干摩擦磨损性能的影响

基于一步法思路,采用金属3D打印机基于激光选区熔化（SLM）技术制备表面带有凹坑织构的TC4钛合金试样,采用光学相机、超景深显微镜和扫描电镜观察织构成形情况,利用激光共聚焦位移测试仪和显微维氏硬度计分别测试表面粗糙度和表面硬度,在干摩擦条件下采用摩擦磨损试验仪考察不同载荷下织构密度对TC4钛合金试样摩擦学性能的影响,并使用扫描电镜对摩擦实验前后的表面形貌进行分析。研究结果表明：一步法SLM成形能够在TC4钛合金表面获得成形良好的直径500 μm的织构;随着织构密度的提高,钛合金试样表面粗糙度增大,表面硬度有所降低;干摩擦条件下,提高TC4钛合金试样织构密度有利于磨屑的收集从而减少试样的三体磨损,提高载荷有利于改善摩擦副接触状态;5 N载荷下40%织构密度试样的平均摩擦因数和磨痕宽度均最小,与无织构试样相比,平均摩擦因数和磨痕宽度分别降低12%和16%;40%织构密度下,载荷提高会引起摩擦因数的降低和磨损量增大,磨损表面犁沟和片状剥落增多。在干摩擦条件下,3D打印一步法制备的表面织构可以显著改善TC4钛合金的磨粒磨损和黏着磨损。     

Loosening Evaluation of Bolted Joints Modified by Fine Particle Bombardment under Transverse Cyclic Loading

ABSTRACT

The objective of this article is to evaluate the loosening behavior of bolted joints modified by fine particle bombardment (FPB) under transverse cyclic loading. FPB treatment was conducted to thread surfaces of both the bolt and the nut. Self-loosening experiments were then performed on the bolted joint with high, medium, and low preload using a fatigue testing machine. The test results show that fretting wear occurs at the thread surface under transverse cyclic loading, which leads to gradual self-loosening of bolted joints without the rotation of the nut. FPB treatment alleviates thread wear by increasing the surface hardness and reducing the friction coefficient between threads, thereby improving the anti-loosening ability of bolted joints. After FPB treatment, the bolted joints with a lower preload exhibited a greater relative improvement in anti-loosening ability than those at a higher preload.     

Tribological Properties of Lubricating Films on the Al-Si Alloy Surface via Laser Surface Texturing

Dimpled textures were prepared by using a pulse solid laser on the surface of Al-Si alloy. The combination of laser surface texturing (LST) and MoS₂ solid lubricant as well as their tribological properties were investigated in this article. The obtained friction and wear data were critically analyzed to investigate how the parameters of texture influence the tribological performance of Al-Si alloy. Furthermore, morphological investigations of the transfer layers on the worn surfaces were performed and the wear mechanisms are discussed. The results show that the combination of LST and solid lubricant improves the tribological characteristics of Al-Si alloy. The friction coefficient of Al-Si alloy: steel friction pairs can be reduced to 0.15 under dry friction. The lubrication mechanism is attributed to a synergetic effect of providing solid lubricant and traps wear debris in the dimples. It was found that the optimum density of structure was 37% for excellent tribological properties.     

超声滚压对铝合金表面质量和耐磨性影响研究

使用多珠平面滚压加工刀具对叉车举升液压缸表面实施滚压加工和超声滚压加工。通过激光共聚焦显微镜、光学显微镜和显微硬度仪对加工后的试样进行表面三维形貌、金相组织和硬度表征的研究。开发相应的分子动力学模型并对加工前后的试样进行干摩擦试验,对比研究超声滚压对液压缸铝合金表面摩擦磨损性能的影响。试验结果表明,与滚压加工相比,超声滚压加工进一步降低了表面粗糙度。磨损结果表明,超声滚压加工改变了试样表面的微观结构,改变了试样的磨损机制,提升了试样的抗磨损性能,可有效提高液压缸使用寿命,降低泄漏量。     

Relation between scuffing resistance and the increase in surface hardness during tests under conditions of rolling/sliding

The effect on scuffing resistance of a change in the condition of the rubbing surfaces, especially surface hardness, was investigated using a two-disc machine. Scuffing resistance increased with increasing surface hardness during testing. The increase of surface hardness by work hardening is more beneficial in preventing scuffing than is a change in carbon content or heat treatment. Work-hardened disc surfaces allow surface film formation as a result of plastic deformation. Materials with large Meyer indices and high surface hardness are less prone to scuffing.     

船舶柴油机气缸套拉缸机理的试验研究

根据模拟试验的相似准则设计磨损试验,研究对船舶航行安全构成严重威胁的异常磨损现象,例如拉缸和咬缸。试验结果表明硬化相的性能和含量与试验所选用的材料耐磨性相一致,且随着载荷的增加,材料发生拉毛的时间呈指数关系下降,本文根据摩擦副三滑磨面接触模型,进而提出摩擦界面温度升高导致粘着以及摩擦副表面的强烈摩擦导致硬化相的碎裂甚至折断等因素是气缸套异常磨损的根本原因,为预防气缸套拉缸或者咬缸提供了理论依据。     

The effect of phosphating on the friction and wear properties of grey cast iron

The friction and wear resistance of two commercial manganese phosphate coatings have been evaluated. Grey cast iron wear pins were treated by the two processes and were tested by sliding against a steel disc, under both lubricated and dry sliding wear conditions.Phosphating increases the sliding distance to scuffing as well as the scuffing load, whilst marginally reducing the coefficient of friction. No advantage was found in phosphating dry sliding surfaces.Phosphating reduces the likelihood of adhesive wear in marginal or poorly lubricated sliding couples. The choice of phosphate coating is primarily dependent on the surface finish of the sliding counterface; thin coatings are suitable if the counterface is smooth but thicker coatings are superior against rougher surfaces.     

Mechanism of abrasive wear of Al-Si hypoeutectic alloycontaining 5 vol% fly ash

Fly ash, an inexpensive resource material, has been introducedinto Al-Si hypoeutectic alloy (A356) to make low-cost compositeswith decreased density and improved hardness and abrasive wearbehavior. The mechanisms of abrasive wear of stir-cast A356-5vol% fly ash composite were discussed based on the results ofwear tests of composites and the A356 base alloy. Scanningelectron microscopy was used to investigate the morphology ofthe worn surfaces, wear debris for both composite and A356 basealloy. The subsurface of the worn samples was also observed.These morphology observations provide a method to understand theabrasive wear and friction mechanism of the composites showing that the base alloy wears primarily by microcutting but thecomposite wears by microcutting and delamination caused by crackpropagation below the rubbing surface through interfaces of flyash and silicon particles with the matrix.     

Condition monitoring of marine diesel engines through ferrographic oil analysis

The effect of surface hardness on scuffing was investigated using a two-disc machine. The changes in the surface conditions, especially surface roughness, surface hardness and the formation of an oxide film, in the running-in process have a marked influence on the scuffing resistance. Therefore a hard disc does not always have a high resistance to scuffing. In this investigation, quenched discs of the highest surface hardness, in which the improvement in surface roughness and the formation of an oxide film are expected to be small, offered the poorest resistance to scuffing. By contrast, annealed discs of the lowest hardness, in which a diminished surface roughness and an increased surface hardness caused by the work hardening that necessarily accompanies the formation of an oxide film are expected, exhibited a considerably higher resistance to scuffing.     

Effect of the Graphite Content on the Tribological Behavior of Al/Gr and Al/30SiC/Gr Composites Processed by In Situ Powder Metallurgy (IPM) Method

The influence of graphite content on the dry sliding wear characteristics of Al6061/Gr composites along with Al6061/30SiC/Gr hybrid composites has been assessed using a pin-on-disc wear test. The composites with different volume fraction of graphite particles up to 13% were processed by in situ powder metallurgy (IPM) technique. The porosity and hardness of the resultant composites were also examined. It was found that an increase in the graphite content reduced the porosity, hardness, and friction coefficient of both types of composites. The hybrid composites were more porous and exhibited higher hardness and lower coefficient of friction at identical graphite contents. The increased graphite content in the range of 0–13 vol.% resulted in increased wear rate of Al/Gr composites. The Al/30SiC composite exhibited a lower wear rate as compared with the base alloy and graphite addition up to 9 vol.% improved the wear resistance of these hybrid composites. However, more graphite particles addition resulted in increased wear rate. SEM micrographs revealed that the wear mechanism was changed from mostly adhesive in the base alloy sample (Al/0Gr) to the prominently abrasive and delamination wear for Al/Gr and Al/SiC/Gr/composites.     

滑动速度对油润滑表面胶合磨损的影响

在油润滑条件下,钢对钢摩擦副的胶合摩损不仅取决于润滑油膜是否破裂,而且取决于在摩擦表面上化学反应膜的形成情况。本文研究了在油润滑条件下滑动速度对钢摩擦副胶合的影响。在低滑动速度下摩擦表面易于形成反应膜,油膜破裂后并不直接发生胶合。胶合发生在高温、高摩擦系数的恶劣条件下。在高滑动速度下油膜破裂后很容易发生胶合,发生胶合前的表面温度和摩擦系数都比较低。     

Scuffing behaviour of salt-bath nitrided steel in loaded lubricated sliding/rolling contacts

The modified 3 in (76.2 mm) David Brown disc machine has been used to investigate the effect on scuffing performance of grinding away various amounts from the surface of nitrided steel discs. The results revealed a systematic deterioration in scuffing resistance as the surface nitrogen concentration decreased, but quantitative correlation between these parameters was hindered by the inadequacies of electron probe X-ray microanalysis as a tool for measuring low nitrogen concentrations. It was concluded that there is no safe depth to which Tenifer-treated (salt-bath nitrided) C15 steel can be ground without impairing its scuffing performance. Other disc tests were carried out to assess the effect on scuffing of phosphate treatment and oil formulation. Results showed that, while phosphate treatment is valuable when running against untreated steel, it is of no benefit against Tenifer-treated steel. On the other hand, the formulation of the lubricant was found to improve the scuffing resistance of Tenifer-treated steel     

高频感应熔覆NiTiFe合金涂层摩擦学性能研究

为增强金属材料表面的耐磨性能,采用高频感应熔覆技术,在HT300基底表面制备出NiTiFe合金涂层;利用扫描电子显微镜(SEM)、能谱仪(EDS)、显微硬度计和X射线衍射仪(XRD)对NiTiFe合金涂层的微观组织、元素组成、硬度、相组成和与基底的结合情况进行表征与分析;通过摩擦磨损试验机对涂层的摩擦学性能进行测试,对其摩擦磨损机制进行分析。结果表明：涂层组织致密,无裂缝和空隙,成型质量良好,平均厚度达到0.7 mm,与HT300基底实现了冶金结合;涂层中主要包含Fe2Ti、Fe6.94Ti0.36和Ni3Fe三种相,Fe元素的加入使涂层的晶格发生畸变,硬度提高,平均硬度达到997.36HV,约为HT300基底平均硬度值的5倍。通过摩擦磨损试验发现,试验前期,NiTiFe合金涂层与对摩副之间的摩擦因数较低,维持在0.2左右,对摩副的失效导致摩擦副之间的接触形式发生改变,摩擦因数产生阶跃;随着载荷的增加,涂层上呈现的磨痕宽度在不断增加,对摩副由于磨损造成的材料去除后暴露出的面积也在不断增大。摩擦磨损试验后,NiTiFe合金涂层摩擦表面光滑平整,仅出现了轻微的磨粒磨损,磨损体积远小于对摩副...     

船舶柴油机缸套活塞环微观滑动接触模型研究

本文根据模拟试验的相似准则设计了磨损试验，得出硬化相的性能和含量与试验所选用的材料在性和一致，且随着载荷的增加，材料发生拉毛的时间呈指数关系下降。在此基础上建立了摩擦配对副三滑磨面接触模型，为更好地解释内燃机气缸套及活塞环的磨损现象提供了理论依据。     

胆甾醇润滑添加剂的摩擦噪声与胶合分析

在N15机械油中添加胆甾醇,用标准的立式万能摩擦磨损试验台实验分析了N15机械油、N15油机械 胆甾醇的摩擦磨损性能。针对磨合阶段、稳定磨损阶段、胶合失效与摩擦噪声进行分析。结果表明,在磨合阶段摩擦因数有较大变化,随后的稳定磨损阶段中摩擦因数变化减小;在摩擦副出现胶合失效前,摩擦副的摩擦因数急剧上升;N15机械油 1.7%胆甾醇的抗胶合性能较好,但N15机械油 0.106%胆甾醇的摩擦噪声特性较好;胆甾醇添加剂可以显著改善N15号机械油的抗胶合能力。     

矿用钛合金钻杆表面复合强化与摩擦性能研究*

为提高矿用钛合金钻杆的耐磨性能,以低成本粉末冶金Ti-Al-Fe-Mo合金为研究对象,采用表面机械碾磨与固相渗碳相结合的创新方式对其表面进行复合强化处理,研究不同表面碾磨道次加渗碳处理的钛合金表面的微观组织及其显微硬度。以氮化硅球为摩擦对偶,对表面复合强化钛合金样品进行往复式滑动摩擦试验,研究钛合金表面强化层对其磨损量、摩擦因数、表面磨痕微观组织的影响规律。结果表明：表面机械碾磨方法可以在粉末钛合金表面形成梯度纳米晶结构;钛合金经过表面机械碾磨处理后可显著提高表面渗碳的深度和均匀度;经表面机械碾磨与固相渗碳复合强化处理的钛合金,其磨损量相比于单一表面渗碳的钛合金降低了近58%。表面复合强化的钛合金摩擦磨损机制以疲劳磨损、黏着磨损、氧化磨损和少量的磨粒磨损为主。     

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.     

Structure and tribological behavior of submicrocrystalline titanium modified with nitrogen ions

The influence of combined treatment including intensive plastic deformation and ion-beam nitriding on the structure and tribological behavior of VT1–00 titanium alloy is studied. Intensive plastic deformation of titanium is shown to result in the formation of submicrocrystalline structure and 50–60% greater hardness of the alloy with tribological properties remaining unchanged. Implantation of nitrogen ions into titanium at 620–820 K results in the formation of a hard solution in the matrix α phase, which provides an increase in the microhardness of the modified layer up to 3500–3700 MPa and an increase in the alloy wear resistance by about 30 times, as well as a decrease in the coefficient of friction by 40%.     

Scuffing resistance of phosphate esters II: Effect of applied voltage

The scuffing resistance of tricresyl phosphate under severe conditions of lubrication was investigated using a reconstructed Timken machine. Although the iron phosphate formed on rubbing surfaces is effective in preventing scuffing under mild lubricating conditions, transformation to iron phosphide is essential to prevent scuffing under severe lubricating conditions. The friction polymer produced during tests is beneficial in increasing scuffing resistance.The formation of surface films is influenced by the electric current flowing between the rubbing surfaces as a result of the formation of a galvanic cell or an externally applied voltage. To prevent scuffing it is beneficial to promote film formation on a surface operating under more severe lubricating conditions than those of the mating surface. However, excessive promotion of surface film formation by the applied voltage decreases scuffing resistance by preventing film formation on the mating surface.