Effects of coating thickness and residual stresses on the bond strength of ASTM C633-79 thermal spray coating test specimens

Wire-arc-sprayed nickel-aluminum is widely used in the aircraft industry for dimensional restoration of worn parts and as a bond coat for thermal barrier coatings and other top coats. Some repair applications require thick coatings, which often result in lower bond strength. A mechanism being investigated to ex-plain this decrease in bond strength is the free edge effect, which includes both coating residual stresses and coating thickness. The layer-removal method was used to determine experimentally the residual stresses in wire-arc-sprayed nickel-aluminum coatings of different thicknesses. Bond strength evalu-ations were performed using an improved ASTM C 633-79 test specimen. Finite-element analysis and fracture mechanics were used to investigate the effects of coating thickness and residual stress state on coating bond strength.     

用双层辉光等离子法在钛表面制备的Ti-Pd合金层性能研究

采用双层辉光等离子冶金技术在纯钛表面制备了Ti—Pd合金层。其深度大约为90μm，Pd含量呈梯度变化，并出现了TiPd3，TiPd2，Ti2Pd3，Ti3Pd5，TiPd，Ti4Pd等6种化合物相和Pd相。合金层在100℃的NaCl饱和溶液＋HCl溶液以及40℃的8．6％H2SO4溶液中的耐缝隙腐蚀性能优于Ti0．2Pd合金；在室温80％H2SO4的溶液中，腐蚀速率仅为0．682mm／a，是Ti0．2Pd合金的18．2％：在室温30％HCl的溶液中，表面Ti—Pd的腐蚀速率仅为0．004mm／a，是Ti0．2Pd合金的12．5％。     

Role of platinum in the Na2SO4-Induced hot corrosion resistance of aluminum duffusion coatings

Electrochemical corrosion measurements have been carried out with Pt-containing and Pt-free Al-diffusion coatings on IN 738 LC in a 90Na₂SO₄+ 10K₂SO₄ (mol%) melt at 1173 K. Pt improves the resistance to basic fluxing while there are no significant differences between both coating types in their resistance to acidic fluxing. The corrosion resistance of the Pt-containing coating is also higher in the passive potential region where protective scales rich in Al₂O₃ are formed. The reason for the different behavior of both coating types appears to be related to the high corrosion resistance of the Pt-rich surface layer of the coating and an increased Al₂O₃ content in the scale of the Pt-containing type.     

A novel electroless silver depositing method for magnesium alloys

Depositing silver on magnesium alloy by both electroless plating and organic coatings was studied. The organic coating was made by immersing samples in organosilicon heat-resisting varnish. In this method the organic coating acts as interlayer between the substrate and silver film. When the reaction starts, silver deposits directly on the interlayer. X-ray diffraction and SEM analysis were used to determine the composition and morphology of the interlayer and silver film. The potentiodynamic polarization curves for corrosion studies of coated magnesium alloys were performed in a corrosive environment of 3.5% NaCl（mass fraction） at neutral pH （6.9）. The results indicate that compared with the substrate, the corrosion resistance of coated magnesium alloys increases greatly. Moreover, the method proposed in this work is environmentally friendly, non-toxic chemicals were used. In addition, it provides a new concept for the corrosion inhibition of magnesium alloys.     

Ni-Cr-Fe-Si-B合金涂层及铝青铜基体熔合区组织的研究

采用钨极氩弧焊方法在铝青铜基体上施焊了Ni—Cr-Fe-Si—B合金涂层，并运用金相显微镜、扫描电子显微镜及能谱分析了喷涂层、熔合区及热影响区的组织形貌和成分分布。结果表明，喷焊时，在涂层与基体界面两侧各组元均发生了明显的扩散，Cu、Ni组元间可相互取代，基体融合区组织的基本组成仍为α (α γ2)，但同时也形成了Cu2FeAl7、NiAl3等新相，且融合区组织细小，涂层与基体间为冶金态结合。     

Morphological evolution of primary TiC carbide in laser clad TiC reinforced FeAl intermetallic composite coating

1　INTRODUCTIONIronaluminumbasedonFeAlintermetallicalloywasexpectedtobeanimportantandpotentialhightemperaturematerial,becauseitsgoodresistancetooxidationandcorrosion ,lowdensityandhightem peraturemelting point[12 ] .However ,theintrinsicpropertiesofFeAlintermetallicalloy ,suchaslowductilityandlowfracturestrength ,limiteditsindus trialapplications .Howtoimprovemechanicalproper tiesofFeAlintermetallicalloyandexpanditsindus trialapplicationrealmwasanimportantresearchas pectformaterialworke…     

TBC experience in land- based gas turbines

This paper summarizes prior and on-going machine evaluations of thermal barrier coatings (TBC) for power generation, that is large industrial gas turbine applications. Rainbow testing of TBCs on turbine nozzles, shrouds, and buckets are described along with a test of combustor liners. General Electric Power Generation has conducted more than IS machine tests on TBC turbine nozzles with various coatings. TBC performance has been quite good, and additional testing, including TBCs on shrouds and buckets, is continuing. Included is a brief comparison of TBC requirements for power generation and aircraft turbines.     

机械镀锌过程中先导金属的研究

通过多次试验观察，借助于扫描电子显微镜，结合物理化学、电化学的基础理论知识，对机械镀锌过程中先导金属进行了研究。分析了先导金属在镀层中的分布以及先导金属对机械镀锌形层过程的影响。结果表明机械镀锌过程中的确有先导金属存在，在机械镀锌过程的不同阶段，有着不同的金属起着先导金属的作用。先导金属可以促进机械镀锌镀层的结合强度。     

聚氨酯涂料的技术动向

叙述聚氨脂涂料的类型,各类聚氨脂涂料的特性、聚氨脂涂料的合成及目前聚氨脂涂料的技术进步动向。     

热处理非晶态Ni-P合金镀层的晶化过程

运用电沉积的方法在45钢基体上制备Ni-P合金镀层,使用差示扫描量热法(DSC)和热重法(TG)分析非晶态NiP合金镀层在20℃/min加热速率下的热效应和质量变化。在300℃和400℃分别对镀层进行0,15,30,45,60,75min的热处理,采用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、显微硬度计对镀层进行表征。结果表明:Ni-P合金镀层在加热过程中的放热峰出现在284.8℃处,镀层的质量和元素组成稳定;晶化过程经历了非晶态、亚稳态NiP和Ni5P2、稳定态Ni3P的转变;经过热处理后,镀层的显微硬度显著提高,最大值达1036.56HV,约为镀态的2倍;热处理态镀层的耐NaCl溶液腐蚀性能比镀态有所下降,但两者都比45钢基体好。