Wear resistance of ceramic coating on AZ91 magnesium alloy by micro-arc oxidation

The ceramic coating formed on AZ91 magnesium alloy by micro-arc oxidation （MAO） was characterized. The results show that the ceramic coating （3.4-23 μm in thickness）on the surface ofAZ91 alloy was attained under different micro-arc oxidation treatment conditions, which consist mainly of MgO, Mg2SiO4 and MgSiO3 phases. Nano-hardness in a cross-sectional specimen was determined by nano-indentation experiment. The MAO coatings exhibit higher hardness than the substrate. Dry sliding wear tests for the MAO coatings and AZ91 alloy were also carded out using an oscillating friction and wear tester in a ball-on-disc contact configuration. The wear resistance of the MAO coatings is improved respectively under different treatment time as a result of different structures of ceramic coatings formed on AZ91 alloy.     

等温淬火球铁在铁道车辆耐磨件上的应用研究

考虑到等温淬火球铁具有强度高、韧性好、出色的耐磨性等优点，根据铁道车辆斜楔和衬套配件的服役要求，对等温淬火球铁和传统的金属材料进行了大量摩擦磨损性能比较试验，结果表明，等温淬火球铁斜楔和衬套具有比传统材料高得多的耐磨性，特别是等温淬火球铁斜楔的使用寿命是以往ZG230-450斜楔的6～10倍。因此，等温淬火球铁斜楔和衬套件已在我国铁路车辆上得到了广泛应用。     

Influence of expandable graphite on fire resistance and water resistance of flame-retardant coatings

Expandable graphite (EG) coating and ammonium polyphosphate-pentaerythritol-melamine (APP-PER-MEL) coating were prepared. Thermal degradation and char formation of the coatings were investigated by differential thermal analysis (DTA), thermogravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results have shown that the anti-oxidation and fire-resistant properties of expandable graphite coating containing EG with size of 74 μm are better than those of APP-PER-MEL coating. The static immersion test was applied to study water resistance of the coatings, and the fire protection test and mechanical test were used to analyse heat insulation and mechanical properties of coatings before and after water immersion. The fire-resistant and mechanical properties of APP-PER-MEL coating were severely damaged by water immersion, whereas EG coating containing 8.5% EG with size of 74 μm could retain the good fire resistance even after 500 h water immersion.     

柴油机活塞环耐磨性探讨

通过分析活塞环的基体组织、径向弹力与气缸套的匹配以及对其施行表面处理，以提高活塞环的耐磨性。对活塞环进行调质或渗氮处理，可显著提高其使用寿命。     

稀土镁对铸态高锰钢机械性能的影响

实验了稀土镁对铸态高锰钢机械性能的影响．结果表明，在一定的Ｃ、Ｍｎ、Ｓｉ成分中，加入ＲＥＭｇ合金均使其铸态机械性能有所提高．同时在工业设备上试验证实，加入ＲＥＭｇ的某种成分之高锰钢，在铸态时其耐磨性能、机械性能均已达ＺＧＭｎ１３－１和ＺＧＭｎ１３－２（ＧＢ５６８０－８５）水平并超过了铸态使用的７５Ｍｎ１３     

铈对Fe-Ni-Cr合金耐磨耐蚀性能的影响

根据磨蚀理论,设计了一种含Ce耐磨耐蚀合金,用SEM、X-ray对磨损形貌进行了观察分析.结果表明,加入Ce可以获得致密化程度较高、分布均匀的组织,明显增加了合金碳化物中铬的含量,使碳化物的显微硬度提高,表面有CeFe7新相产生,并引起奥氏体、铁素体含量的增加,改变了试样表面的微观结构,从而提高了Fe-Ni-Cr合金的耐磨耐蚀性能.     

硬质合金堆焊层经热处理后的耐磨性研究

对B、C、N共渗层、碳化钨型硬质合金(D707)堆焊层、高碳高铬铸铁型硬质合金(D618)堆焊层等几种不同表面处理工艺,经相应热处理后的腐蚀磨损性能进行了研究。结果表明,两种硬质合金堆焊层经850 ℃空冷、850±5 ℃油淬+400 ℃回火后,均具有较高的硬度和优异的耐腐蚀磨损性能,且简化了表面处理工艺。     

40Cr钢电火花表面强化层的磨损特性研究

分析了在大接触应力的磨损条件下,表面残余应力和硬度对40Cr电火花强化层耐磨性的影响,探讨了其磨损机理。结果表明:滚动磨损和滚、滑动磨损时,随着试样表层硬度的提高,试样的耐磨性增大;强化层中的残余压应力可以提高强化层的硬度并增强其耐磨性。滚动磨损时,电火花强化层的磨损方式主要为粘着磨损、疲劳磨损和磨粒磨损三种机制;在滚、滑动磨损时,除上述三种机制外,还发生了氧化磨损。     

Study on the Components and Performance of GCrlS Bearing Steel Surface by Gas Multi-elements Penetrating

GAS multi-elements penetrating technology is a newsurface hardening technology developed on the basisof carbonitriding technology.It can not only shortenthe production period,but also improve the mechanicalperformances of the parts,such as torsional strength,flexural strength,wear resistance,and fatigue resistance"'.It features low-temperature multi-elementspenetration that the physical chemistry process ofoxidation-reduction generates the active atoms in thepart surface.In the beginning,the …     

Intelligent cooling structure design of "Z-pins like" silicon rods to enhance the ablation resistance of C/C-ZrC-SiC composites above 2500 °C

In order to improve the ablation resistance of C/C-ZrC-SiC composites by reducing the damage of the protective oxide layer, novel "Z-pins like" silicon rods, which were designed and fabricated by liquid phase sintering, were utilised as a dissipative agent. The microstructure evolution and thermal dissipation behaviour were investigated after ablating above 2500 °C for 300 s. After the "Z-pins like" silicon rods were implanted, the anti-ablative property of the C/C-ZrC-SiC composites was drastically improved by the dissipative thermal protection mechanism. The linear ablation rate of the "Z-pins like" silicon rod-reinforced C/C-ZrC-SiC composite was -0.28 μm/s, which is 112.72% lower than the unmodified composite. Additionally, the actual ablative temperature dropped approximately 357 °C, which enabled abundant SiO₂ to remain in the ablation centre. Furthermore, a dense SiO₂-rich oxide layer with a low oxygen diffusion coefficient is formed that covers the entire ablative surface.