铌合金硅化物涂层的结构及高温抗氧化性

分析了Ｃ－１０３铌合金不同改性成分的Ｔｉ－Ｃｒ－Ｓｉ硅化物涂层在氧化前后组织结构的变化,以及改性成分和涂层结构对高温抗氧化性的影响,结果表明,Ｇｅ、Ｍｏ和Ｗ改性的涂层结构不利于高温抗氧化性能的改善,添加Ｚｒ和Ａｌ后,其涂层组织结构有利干提高高温抗氧化性．     

激光熔化沉积Mo/ Mo2Ni3 Si 金属硅化物合金显微组织与耐磨性

以Mo 、Ni、Si 金属粉末为原料, 利用激光熔化沉积工艺制备出以难熔金属Mo 初生树枝晶为增韧相,以三元金属硅化物Mo₂Ni₃ Si 为基体的金属硅化物耐磨合金, 在室温干滑动磨损条件下测试了合金的耐磨性能。结果表明, 初生树枝晶的体积分数随着Mo 含量的增加而增加, 而硬度却随之降低。由于金属硅化物Mo₂Ni₃ Si的高硬度和难熔金属Mo 树枝晶的高强韧性, 合金在室温干滑动磨损条件下具有良好的耐磨性能。      

Preparation, Microstructure and Age Hardening of Rapidly Solidified Mo-alloys

Various Mo-base alloys with high meltingtemperature were processed into ribbons andfoils by the arc melt-spinning and the arc melthammer-anvil technique. The preparation of ribbonand foil was introduced. The mechanical proper-ties, the surface topology and the microstructureof rapidly solidified Mo-base alloys containingB were examined. A strong grain refinement anda strong age-hardening response were observedon the as-quenched and the age specimens, theprecipitates which cause age hardening wereidentified to be Mo_2B in Mo-B alloys, Mo_2B andZrB_2 in Mo-Zr-B alloys, and Mo_2B and ThB_4 inMo-Th-B alloys. The results indicate that thehigh strength Mo-base alloys containing borideprecipitates can be developed by rapid solidifica-tion technique.     

Mo2Ni3Si/NiSi复合材料涂层的滑动磨损行为

以Mo-Ni-Si合金粉末为原料，使用激光熔敷技术在1Crl8Ni9Ti不锈钢基材表面制备出Mo2Ni3Si／NiSi金属硅化物复合材料涂层．应用OM，SEM，EDS和XRD方法分析了涂层的显微组织．Mo2Ni3Si／NiSi复合材料涂层由初生的Mo2Ni3Si三元金属硅化物树枝晶和枝晶间的Mo2Ni3Si／NiSi共晶组织组成．在常温和高温滑动磨损条件下测试了涂层的耐磨性能．在常温滑动磨损条件下，Mo2Ni3Si／NiSi金属硅化物复合材料涂层的质量损失随着载荷的增加缓慢增加；在高温滑动磨损条件下，Mo2Ni3Si／NiSi金属硅化物复合材料涂层的质量损失随着温度的升高缓慢下降．     

Untersuchung von Oberflächenschutzschichten von Gasturbinenlegierungen

Investigations on protective coatings on gasturbine alloys. It has been found by investigations of specimens of a combustion chamber pilot plant and also by experiences with gasturbines that aluminide or chromium aluminide coatings are only slightly protective under working conditions of industrial gasturbines. Chromium coatings have a distinctive better protective efficacy and are surpassed in this quality by silicide coatings. It was possible to give information on the development of silicide phases on Nimonic 105. Under the conditions of corrosive attack a surface layer of Nickelolivine is formed and the silicide phases are changed in direction of ternary phases. Even when chromium sulfides are formed in the silicide layer the specimens are stable under the test conditions. By investigations on an airfoil made from B 1900 with a protective coating of Aluminium and Silicon the presence is shown of a ternary Laves phase with Silicon.     

Nb-Si基合金高温抗氧化研究进展

Nb-Si基合金具有适中的密度和超高的使用温度,是下一代发动机叶片及高温热端部件的有力竞争者之一,但Nb-Si基合金的高温抗氧化性能不足限制了其应用。主要综述了合金化和硅化物涂层在Nb-Si基合金中的研究进展。在此基础上着重综述了掺杂不同合金元素对Nb-Si基合金中硅化物、抗氧化相和氧化膜的影响,包括提升硅化物相高温氧化能力、促进Al2O3和Cr2Nb形成以阻碍氧原子扩散、通过稀土元素形成黏附性特别高的氧化物以防止氧化层脱落等方面。除此之外,综述了硅化物涂层(MoSi2和NbSi2)的研究进展,包括可通过降低硼硅酸盐的黏度和致密的SiO2薄膜提高Nb-Si基合金的抗氧化性能,并介绍了元素改性硅化物涂层提升SiO2流动性的效果。最后,对该方向的研究进展进行了总结,并对其发展前景和主要发展方向进行了展望。     

Chromium Coating Developed on Mo-Base Materials

Mo-base materials have special use in many fields. One of them is to use as substrate materials for dynamic airproof ring. But the hardness and the wear resistance of Mo-base materials are not good for working under the condition of high temperature and high speed. So it must be cover with chromium coating that has high hardness, excellent wear resistance and high credibility. At present, chrome plating on Mo-base materials is very difficult. So we try to make Chrome coating by LPPS. This paper presented Cr coating that is successfully developed on Mo-base materials by controlling the spraying parameters, especially the air pressure in the spraying chamber. Prepared Cr coating was dense with few pores, bonded well with Mo -base materials. It had high hardness and excellent wear resistance.     

Characterisation of detonation sprayed Mo–Co–Cr–B alloy coatings

Abstract

A novel thermal spray material of Mo–Co–Cr–B with high durability in molten alloys has been developed to utilise for die casting parts and for galvanising bath parts. In the present paper, detonation gun (D gun) spray technique was used to deposit a Mo–Co–Cr–B alloy coating onto 316L stainless steel substrate, and the microstructures and mechanical properties of the coating system were studied using XRD, SEM, tensile test and Vickers microhardness. The results show that the microstructures of the coating consisted of ternary transition metal borides matrix CoMo₂B₂, CoMoB, as well as a little amount of binary borides, MoB and CrB. The ternary borides matrix contained both amorphous phase and nanocrystalline grains with a size of 60±35 nm. The bond strength of the coating decreases with increasing thickness of the as sprayed coatings. The anisotropy in the mechanical properties between the cross-section and plan section of the coatings is examined. Comparing the microhardness and bond strength of detonation sprayed Mo–Co–Cr–B coating with those of HVOF sprayed Mo–Co–Cr–B coating, it can be concluded that the detonation spray process has a better performance than HVOF spray process.     

钼及其合金氧化防护涂层的研究进展

钼及其合金具有较好的高温力学性能和良好的耐腐蚀性能,然而高温氧化问题限制了钼及其合金的应用。分别从涂层体系、涂层结构及涂层的制备工艺3个方面综述了近年来国内外钼及其合金氧化防护涂层的研究进展。在涂层体系方面,目前的研究主要集中在钼的硅化物(如MoSi2涂层)上;在涂层结构方面,对比了各种结构涂层的特点,单一涂层与基体存在热膨胀不匹配问题,使得单一涂层作为高温防护的应用受到限制,然而复合涂层却明显改善了此缺点;在涂层的制备工艺方面,介绍了涂层的各种制备工艺及其优缺点。综合应用各种涂层制备工艺,发展新型复合涂层是今后钼及其合金氧化防护涂层的发展方向。     

微弧氧化处理对多孔Ti-15Mo合金显微结构、耐磨性和耐蚀性的影响

在铝酸盐电解液中对多孔Ti-15Mo舍金进行微弧氧化表面改性.利用SEM和XRD研究多孔舍金微弧氧化涂层的显微结构和相组成.采用显微硬度计、动电位极化曲线和球-盘摩擦磨损仪分析微弧氧化处理对多孔Ti-15Mo合金硬度、耐蚀性和耐磨性的影响.结果表明,微弧氧化处理未改变多孔Ti-15Mo合金原有的孔隙率和孔径,在合金表面和孔隙内壁呈现典型的粗糙多孔微弧氧化形貌.微弧氧化涂层主要由金红石TiO2和Al2TiO5相组成.经微弧氧化处理后,多孔Ti-15Mo合金的表面显微硬度提高了32％,摩擦系数降低了近50％,磨损率大幅度下降,磨损机制由磨粒磨损转变为粘着磨损.微弧氧化处理后多孔Ti-15Mo合金的耐蚀性较基体提高了近1个数量级,微弧氧化陶瓷涂层的保护效率高达90.78％.     

微弧氧化处理对多孔Ti-15Mo合金显微结构、耐磨性和耐蚀性的影响

在铝酸盐电解液中对多孔Ti-15Mo合金进行微弧氧化表面改性。利用SEM和XRD研究多孔合金微弧氧化涂层的显微结构和相组成。采用显微硬度计、动电位极化曲线和球-盘摩擦磨损仪分析微弧氧化处理对多孔Ti-15Mo合金硬度、耐蚀性和耐磨性的影响。结果表明,微弧氧化处理未改变多孔Ti-15Mo合金原有的孔隙率和孔径,在合金表面和孔隙内壁呈现典型的粗糙多孔微弧氧化形貌。微弧氧化涂层主要由金红石TiO_2和Al_2TiO_5相组成。经微弧氧化处理后,多孔Ti-15Mo合金的表面显微硬度提高了32%,摩擦系数降低了近50%,磨损率大幅度下降,磨损机制由磨粒磨损转变为粘着磨损。微弧氧化处理后多孔Ti-15Mo合金的耐蚀性较基体提高了近1个数量级,微弧氧化陶瓷涂层的保护效率高达90.78%。     

钼及钼合金表面高温抗氧化涂层研究现状

钼合金作为新一代重要战略意义的稀有金属,现已广泛应用于冶金、石油、机械、化工、航空航天、核工业等诸多领域,但钼合金在高温环境下易氧化影响了其在航空航天领域的应用。综述了应用于钼及钼合金基体上的金属间化合物、贵金属、耐热合金高温抗氧化涂层体系的不同特点,总结了涂层的不同制备方法并进行了分析对比,展望了国内外钼及钼合金高温抗氧化涂层研究发展趋势,对目前涂层存在的问题及研究现状进行了深入的分析与概述。     

红外高发射陶瓷涂层发射率与厚度关系

红外陶瓷涂层在满足高发射率设计要求的前提下, 应尽量降低涂层厚度, 以满足力学性能要求, 节约原料, 减轻器件重量。因此探索厚度与发射率之间的定量关系, 是高发射率涂层研制中的一项重要内容。本文作者通过在水解法制备的氧化铝溶胶中加入高发射率填料, 制备了高发射率涂料, 并采用喷涂和旋涂工艺得到几种不同厚度的高发射复合陶瓷涂层。通过实验测试考察了复合陶瓷涂层的发射率随涂层厚度的变化规律, 确定了复合涂层的临界厚度。在均匀涂层发射率与厚度关系模型的基础上, 结合Maxwell-Garnett理论, 建立了复合涂层发射率与厚度的理论关系模型。该模型对发射率的计算结果与实验值吻合较好, 表明该模型可以用于实际复合涂层的发射率或临界厚度的预报。      

Effect of temperature and reactivity of molten 55Al–Zn alloy on Co based alloy coatings

Abstract

The short service life of bearings in galvanising industry is a result of a complex set of deterioration mechanisms. This work addressed the effect of temperature and molten bath reactivity on the material of the bearings respectively. Three commercial alloys, the Co–Cr–W Stellite 6 and Co–Cr–Mo–Si Tribaloy (T400 and T800) alloy systems, were deposited by plasma transferred arc on AISI 316L plates. Coatings were evaluated for the effect of temperature exposure on hardness, microstructure and sliding abrasive wear. The reactivity with the molten 55Al–Zn alloy was assessed by immersion tests in an industrial bath. Results showed that exposure at 600°C for 168 h resulted in an increase in hardness, microstructure changes and loss of wear resistance for the Stellite 6 coatings. A superior performance to temperature was shown by Tribaloy T800 with a stable abrasive wear resistance. The three alloys exhibited a strong reactivity with the 55Al–Zn molten bath. An intermetallic layer formed on the coatings as the Al from the bath reacted with elements from the Co based alloys. This reactivity consumed the coatings, causing a reduction on thickness particularly on those processed with the T800 alloy.     

A study on electrodeposited Co–Mo alloys thin films

Cobalt–Molybdenum (Co–Mo) induced electrodeposition has been studied from a sulphate bath on Ru electrodes at pH 4. The conditions of electrodeposition of Co–Mo alloys were determined using the cyclic voltametry at different ions concentration ratios. The theoretical model of Scharifker-Hills was used to analyse the current transients for studying the first stage of nucleation of Co–Mo alloys. The electrodeposited coatings were analysed by scanning electron microscopy, X-rays diffraction and alternating gradient force magnetometer techniques. The cyclic voltametry shows that the codeposition of Co–Mo alloys was accompanied by concurrent reactions such as the formation of the molybdenum oxides and the hydrogen evolution reaction. For the electrodeposited Co–Mo, the nucleation is in good agreement with the instantaneous nucleation and three-dimensional (3D) diffusion-limited growth. Co–Mo thin films of an hcp structure have been obtained, and the electrodeposition parameters such as the applied potential have a great influence on the structure, morphology and magnetic properties.     

CHEMICAL VAPOR DEPOSITION OF SILICON ONTO IRON AND STEEL SUBSTRATES: OXIDATION AND CORROSION PROPERTIES OF COATED MATERIALS

The influence of the gaseous phase composition (SiH₄ or SiCI₄ diluted with argon or hydrogen), used for chemical vapor deposition of silicon onto two different substrates (pure iron or low chromium mild steel) is investigated. Depending on the chosen process, two types of coatings are developed: either a very adherent, non-porous solid solution containing up to 6 to 7 wt. % Si, or a Fe₃Si iron silicide (14.35 wt. %). This solid solution coating considerably improves the oxidation resistance properties of steels at temperatures up to 800° C. This beneficial effect was not observed on the corrosion behavior of treated samples in sulfuric acid solutions. In contrast, the Fe₃Si iron silicide has the same outstanding corrosion resistance that the silicon-rich cast alloys have in very severe environments such as boiling concentrated sulfuric acid. But this remarkable behavior is certainly limited in other mediums by the open porosity of the coating, inherent to the chemical vapor process.     

Nb-Si基合金表面Mo-Si-B涂层制备及抗氧化性能

为提高Nb-Si合金的抗高温氧化性能,在其表面制备Mo-Si-B涂层。通过Thermo-Calc计算的方法,从热力学角度分析NaF和AlF_3两种激活剂对Si-B二元共渗的影响。结果表明:以NaF为激活剂时可以实现Si-B的二元共渗,而以AlF3为激活剂时,难以实现Si-B的二元共渗。通过爆炸喷涂结合包埋渗的方法在Nb-Si合金表面成功制备Mo-Si-B涂层,涂层主要由有弥散硼化物分布的MoSi2外层和未反应的Mo内层构成。涂层在1250℃氧化100h后涂层的氧化增重仅为1.52mg/cm~2,良好的抗高温氧化性能是由于涂层在高温氧化过程中形成了一层具有保护性的硼硅酸盐层。     

AZ91D镁合金热处理与微弧氧化的交互作用

随着AZ91D镁合金微弧氧化反应的进行,膜层逐渐增厚,膜层表面的喷射孔洞和喷射沉积物粗大化,膜层表面粗糙度增大.微弧氧化反应时膜层内部的应力集中会使膜层萌生微裂纹.对基体进行固溶处理后可以改善其微弧氧化膜层中微裂纹的数量和形态以及膜层表面的粗糙度,并能提高微弧氧化膜层的生长速率,同时降低微弧氧化过程的能耗.时效处理会使微弧氧化膜层中的残余应力得以释放,微弧氧化膜的形貌没有发生明显改变,即膜层表面的微裂纹在数量和形态上仍好于未经热处理基体膜层.微弧氧化处理不会引起基体组织的显著变化.在硅酸盐溶液体系中,AZ91D镁合金表面参与微弧氧化反应的Al比Mg少得多,同时还伴随着一个溶液中的Si向镁合金基体内部渗透的过程.     

NbMoTiVSi_x refractory high entropy alloys strengthened by forming BCC phase and silicide eutectic structure

In order to improve mechanical properties of refractory high entropy alloys,silicide was introduced and NbMoTiVSi_x(x=0,0.1,0.2,0.3,and 0.4,molar ratio) refractory high entropy alloys are prepared by vacuum arc melting.Phase composition,micro structure evolution and mechanical properties were systematically studied.Results show that the silicide phase is formed in the alloys with addition of silicon,and the volume fraction of silicide increases from 0 to 8.3 % with increasing of silicon.Microstructure observation shows that the morphology of dendrite changes from columnar to near equiaxed,eutectic structure is formed at grain boundaries and composed of secondary BCC phase and silicide phase.The average length of the primary and second dendrites decreases with the increasing of silicon.Whereas,the ratio of eutectic structure increases from 0 to 19.8 % with the increment of silicon.The refinement of microstructure is caused by heterogeneous nucleation from the silicide.Compressive tests show that the yield and ultimate strength of the alloys increases from 1141.5 MPa to 2093.1 MPa and from 1700.1 MPa to 2374.7 MPa with increasing silicon content.The fracture strain decreases from 24.7 %-11.0 %.Fracture mechanism is changed from ductile fracture to ductile and brittle mixed fracture.The improvement of the strength is caused by grain bounda ry strengthening,which includes more boundaries around primary BCC phase and eutectic structure in grain boundary,both of them is resulted from the formation of silicide.     

Mo含量对CoCrFeNiMo高熵合金组织及耐蚀性能的影响

高熵合金由于具有优异的机械性能及耐蚀性能在涂层工业领域备受关注。采用同步送粉激光熔覆技术在Q235钢表面制备了CoCrFeNiMo_x高熵合金涂层,研究了涂层的组织结构和耐蚀性能,并结合第一性原理计算分析了涂层耐蚀机理。研究结果表明：CoCrFeNiMo_0.1、CoCrFeNiMo_0.2高熵合金涂层是由fcc相组成,而CoCrFeNiMo_0.3高熵合金涂层则由fcc相和σ相组成。合金的晶粒主要呈树枝晶,枝晶间富集Cr、Mo元素,枝晶内富集Co、Fe元素。在3.5%(质量分数)NaCl溶液中,CoCrFeNiMo_x高熵合金涂层具有优良的综合耐蚀性能;并且随着Mo元素含量的增加,涂层的腐蚀电位正移,腐蚀电流密度减少,钝化区间变长,阻抗弧半径增大,电极反应阻力增强。通过第一性原理计算证明,涂层较高的耐蚀性能与表面致密的钝化膜形成密切相关。