Comparison of interfaces in Ti composites reinforced with uncoated and TiB2/C-coated SiC fibres

Interfaces play an important role in determining the mechanical properties of composite materials. The interfaces established between a titanium-alloy matrix (Ti-6Al-4V) and uncoated and TiB₂/C-coated SiC fibres are analysed by scanning electron microscopy, transmission electron microscopy and X-ray techniques. Emphasis is placed upon the interfacial morphology and microstructure, identification of reaction products, and the stability of the coating layer. Complex multi-reaction layers are observed frequently in the interfacial zones. Previous, often contradictory, reports about the interlayers are reviewed. Experimental observation demonstrates that the type and distribution of interlayers vary in a given system, due to prolonged treatment of the samples at temperature. The formation and distribution of the interlayers are discussed further, with respect to these and previous findings. Methods of reducing interfacial reactivity are discussed.     

大型桁架展开机构热控涂层设计和热变形分析

为控制大型桁架展开机构在低地轨道(Low Earth Orbit,LEO)上的热变形,建立相应的热分析有限元模型,提出3种热控涂层备选方案.根据不同方案计算出机构在LEO上运行4个周期的瞬态温度场,并以最后一个周期的瞬态温度场为基础计算机构的热变形.对热变形的结果进行比较,选取变形值最小的热控涂层方案进行优化,使3根主梁的温差达到最小,从而有效控制桁架展开机构的热变形.     

Simultaneous chromizing-aluminizing coating of austenitic stainless steels

Chromium and aluminum were simultaneously co-deposited by diffusion into austenitic stainless steel substrates, by a single-step, pack-cementation process. The mechanism for the formation of diffusion-coated products on 304 and 316 stainless steels and on Incoloy 800 is discussed. The morphologies of the phases formed at the surface, i.e., an external beta layer and an underlying multiphase interdiffusion zone, are presented. The formation of the brittle, , outer layer was minimized by variations in the pack composition and activator. The coated 304 and 316 steels exhibited excellent scaling resistance upon oxidation in air at 1000°C.     

Corrosion behaviour of Ni-Zr-Ti-Si-Sn amorphous plasma spray coating

Ni₅₉Zr₂₀Ti₁₆Si₂Sn₃ amorphous material was deposited by a vacuum plasma spraying technique onto steel and copper substrates in order to investigate their behaviour in a corrosive environment. For comparison, the same alloy was prepared as amorphous ribbons by melt spinning. The amorphous nature of the coatings and ribbons was characterized by XRD, DSC and TEM, while XPS and AES analyses were performed to understand the origin of passivation and mode of corrosion. The corrosion behaviour of the coating was studied in H₂SO₄ and HCl solutions open to air at room temperature. Potentiodynamic polarisation and galvanic coupling tests were carried out on the substrate and the coating. It was found that the formation of Zr-, Ti- and Si-rich passive oxide layers provide a high corrosion resistance in H₂SO₄ solution while the breakdown of the passive layer by chloride ion adsorption was responsible for pitting corrosion of the Ni₅₉Zr₂₀Ti₁₆Si₂Sn₃ amorphous ribbons in HCl solution. Galvanic corrosion was the dominant corrosion mechanism for the coating/copper hybrid structure, in contrast to the Ni₅₉Zr₂₀Ti₁₆Si₂Sn₃ amorphous coating, which efficiently protected the steel substrate in the corrosive environment.     

Ni－Fe－Cr－B－Si涂层超塑扩散焊接的强化效应及耐磨性

研究了Ｎｉ－Ｆｅ－Ｃｒ－Ｂ－Ｓｉ合金涂层超塑性扩散焊接及焊接后的强化效应。通过对涂层的组织结构分析、硬度及耐磨性能的测试表明，当基材（５ＣｒＭｎＭｏ钢）与涂层产生协调超塑变形时，涂层原颗粒间、涂层与基材结合界面完全焊合。超塑焊合后的涂层比高频重熔及火焰重熔涂层硬度（ＨＶ）提高１００－１５０，耐摩擦磨损性能提高３０％。指出，沉淀强化、细晶强化及晶内位错密度增加是引起涂层强化效应和提高耐磨性的主要因素。     

Stannate and permanganate conversion coatings on AZ31 magnesium alloy

The formation of stannate and permanganate–phosphate conversion coatings on AZ31 magnesium alloy was investigated in situ by EIS measurements and their protective performances were studied by different electrochemical techniques in diluted (0.05 M) sodium sulphate solution.The influence that short or long treatment times exert on the performances of such conversion coatings is discussed. While permanganate–phosphate baths always built layers characterized by penetrating cracks, long stannate baths produced layers without interconnected porosity, but were defective. This accounted for the initial greater protectiveness achieved with the stannate treatment; nevertheless, the easy penetration of the electrolytic solution through such a layer quickly decreased its corrosion resistance.     

弹链粉末涂装可行性探讨

通过炮用弹链粉末静电喷涂工艺试验,验证了弹链粉末涂装的可行性。粉末涂装工艺能够提高炮用弹链的防蚀性,简化工序。     

钢表面化学气相沉积TiC晶体的择优取向

本文用化学气相沉积(CVD)法,以TiCl_4-CH_4-H_2为原料气体,在不锈钢表面获得了致密的TiC膜.研究了TiC的成膜速度、表面形貌和晶体择优取向与沉积条什的关系.结果表明,沉积温度T_(dep),碳钛比CH_4/TiCl_4强烈地影响了TiC的成膜速度、表面形貌和晶体择优取向.CH_4/TiCl_4低时,TiC晶体的择优取向为(220):而CH_4/TiCl_4高时,TiC晶体的择优取向为(200).TiC晶体的择优取向主要取决于气氛中活性碳的平衡浓度。     

纳米Cr颗粒对Ni-Mo复合镀层性能的影响

为了研究纳米Cr颗粒对Ni-Mo复合镀层性能的影响,采用脉冲电沉积方法制备具有不同Cr含量的Ni-Mo复合镀层.利用扫描电子显微镜和X射线衍射仪分别观察和分析复合镀层的组织形貌及结构.采用电化学测试和X射线光电子能谱研究复合镀层的析氢性能和耐蚀性能.结果表明:随着镀液中纳米Cr颗粒含量的增加,镀层晶粒得到细化,析氢过电位增大,复合镀层析氢性能得到提高;当镀液中纳米Cr颗粒含量为20 g/L时,复合镀层表面钝化膜中MoO₃含量较高,且可与Cr产生协同效应,因而复合镀层具有较好的耐蚀性能;但随着镀液中纳米Cr颗粒含量的进一步增加,复合镀层中沉积的Cr元素含量降低,复合镀层的析氢性能和耐蚀性能均降低.因此,当镀液中纳米Cr颗粒含量为20 g/L时,复合镀层具有较好的析氢性能和耐蚀性能.     

表面工程技术在导弹武器装备维修中的应用

本文主要介绍铝/F_(46),协合涂层新技术、复合电刷镀Ni—PTFE新工艺、DJB—823电接触保护剂及三防电子器件绝缘清漆在二炮导弹武器装备维修中的应用。