Experience with platinum aluminide coatings in land-based gas turbines

Hot-corrosion crucible tests with salt mixtures which simulated actual blade deposits were carried out to evaluate the potential of platinum-modified aluminide coatings for application in advanced industrial gas turbines. In comparison with simple aluminide coatings, a significantly improved resistance against hot corrosion at intermediate temperatures was found. At the highest turbine-operating temperature, coating life exceeds that of conventional plasma-sprayed NiCrSi coatings. Actual engine test results are presented which confirm the beneficial role of platinum. However, the susceptibility of platinum aluminide coatings to crack formation and propagation may make them unsuitable for application to rotating blades.     

Composite calcium phosphate coatings with sustained Zn release

Zinc-substituted tricalcium phosphate/fluoridated hydroxyapatite (ZnTCP/FHA) biphasic composite coatings and Zinc containing fluoridated hydroxyapatite (ZnFHA) coating were prepared on Ti6Al4V substrates through a modified sol-gel method. The release of zinc ions from these coatings was characterized through a designed cycled immersion test: the coatings were soaked in the TRIS solution with pH of 7.25 at 37 °C for 96 h (one cycle). This process was repeated twice with the solution refreshed at the end of the each cycle. The Zn concentrations were measured at a 24-hour interval during the first cycle and at the end of each cycle. The results indicated that ZnTCP/FHA coatings released Zn at a rather slow and sustained rate while ZnFHA coatings released Zn at a rapid and therefore unsustained rate. This Zn release behavior difference is attributed to the different chemical states of Zn in the coatings. The current results demonstrated that the designed biphasic composite approach could potentially be a good way to tailor the release of Zn through combinations of different Zn chemical states, with the durability of the coatings not impaired.     

溅射CoCrAlY涂层对NiAl金属间化合物热腐蚀性能的影响

本文采用电化学及物相分析技术研究了NiAl和NiAi(Fe)金属间化合物在熔融NaCl-(Na,K)_2SO_4中的腐蚀行为及溅射CoCrAlY涂层对NiAi(Fe)耐蚀性能的影响。结果表明,NiAl和NiAl(Fe)合金的耐蚀性能极差,硫化-氧化是合金腐蚀破坏的根据本原因。合金表面不能形成Al_2O_3保护层,Al的氧化相反会加速合金腐蚀。向NiAl合金中添加Fe可在一定程度上改善NiAi(Fe)的耐蚀性能。     

Composite ceramics thermal barrier coatings of yttria stabilized zirconia for aero-engines

Composite ceramics thermal barrier coatings(TBCs) are widely used in the aero-engines field due to their excellent thermal insulation, which improves the service life and durability of the inherent hot components. The most typical, successful and widely used TBCs material is yttria stabilized zirconia(YSZ). In this paper, fabrication methods, coating structures, materials, failure mechanism and major challenges of YSZ TBCs are introduced and reviewed. The research tendency is put forward as well. This review provides a good understanding of the YSZ TBCs and inspires researchers to discover versatile ideas to improve the TBCs systems.     

Composite ceramic-metal coatings by means of combined electrophoretic deposition and galvanic methods

A method based on the combination of electrophoretic and galvanic deposition techniques has been developed to fabricate metal-ceramic composite coatings on metallic substrates. A ZrO₂-Ni composite coating with interpenetrating microstructure was produced on stainless steel plates. For electrophoretic deposition of the ceramic component, a non-aqueous suspension consisting of zirconia nanoparticles, ethanol and addition of 4-hydroxybenzoic acid was optimised by electrokinetic sonic amplitude (ESA) measurements. The zirconia deposits were partially sintered to create an open porous structure (porosity = 40–50%), which was subsequently filled with Ni by galvanic deposition. The bonding strength between the composite coating and the stainless steel substrate was improved by a final heat-treatement at 950°C for 3 h which promoted the diffusion of Ni into the steel substrate and the formation of a diffusion interlayer. The high adhesion strength of the composite coating to the stainless steel substrate after the diffusion bonding heat-treatment was confirmed by 3-point flexural strength tests. The coating exhibited a homogeneous interpenetrating microstructure with hardness values >6 GPa.     

Ni3Al金属间化合物及溅射CoCrAlY涂层的高温热腐蚀

研究了Ｎｉ３Ａｌ金属间化合物及溅射ＣｏＣｒＡｌＹ涂层在９００～９５０℃空气中，表面存在（Ｎａ，Ｋ）２ＳＯ４盐膜时的热腐蚀行为，结果表明，Ｎｉ３Ａｌ遭受严重的热腐蚀，溅射ＣｏＣｒＡｌＹ涂层可以通过在表面迅速形成保护性Ａｌ，Ｃｒ氧化膜而显著改善Ｎｉ３Ａｌ的耐热腐蚀性能。     

Fabrication of Titanium Diboride-Cu Composite by Self-High Temperature Synthesis plus Quick Press

1. IntroductionTitanium diboride ceramic has some special proper-ties, such as high melting points, high hardness, highelectrical and thermal conductivity. These special prop-erties make it has a great potential to be used as contactmaterials. However, this application is still limited forpoor sinterability and brittle of TiB2[1~3]. To improve itssinterability and toughness, some metals were selected asadditives for liquid phase sintering of TiB2. Metals likeFe, Co and Ni were studied in m…     

The influence of platinum on the oxidation and sodium sulfate induced hot corrosion of NiAl diffusion coatings

Abstract

Oxidation and corrosion properties at 900°C of two coatings, one containing platinum and the other platinum-free, on IN792 were investigated. During the corrosion exposures, sodium sulfate salt was situated in the furnace together with the coated specimens. The temperature of the salt was kept above its melting point but lower than the temperature of the coating i.e. 900°C. The exposure times ranged from 100 to 1000 h. The formed oxide scales were studied by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy and scanning transmission electron microscopy techniques. It is shown that the presence of Pt improves the protective properties of the coating against corrosion. The propagation stage of corrosion on the platinum-free coating is reached already after 100 h of exposure. On the other hand the scale formed on the platinum-rich samples still appeared to be protective even after 500 h. The details concerning structure and chemistry of the scales formed are presented and discussed.     

The effect of yttrium content on the oxidation-induced degradation of NiCoCrAlY coatings and the influence of surface roughness on the oxidation of NiCoCrAlY and platinum aluminide coatings

Abstract

It has been found that the yttrium content of NiCoCrAlY coatings affects the useful lives of such coatings during cyclic oxidation. In particular, NiCoCrAlY coatings with 0.1wt% yttrium have more than twice the lifetime at 1100°C compared to NiCoCrAlY coatings with 0.5wt% yttrium. The mechanism by which the yttrium concentration influences the degradation of NiCoCrAlY coatings will be described. It has also been observed that the adverse effect of yttrium can be inhibited by reducing the roughness of the coating surface. The influence of surface condition on the oxidation of yttrium in NiCoCrAlY coatings will be examined in detail and the effects of surface roughness on the oxidation of NiCoCrAlY and platinum aluminide coatings will be compared. Finally the effects of yttrium in the substrate alloy on the oxidation of platinum aluminide coatings will be discussed.     

Frictional property with preferred crystal orientation of platinum oxide and palladium oxide coatings synthesized by combinatorial sputter coating system

The combinatorial sputter coating system (COSCOS) has been newly developed, that can fabricate various kinds of coatings under precisely controlled lots of conditions such as selection of sputter gas and gas pressure, gas partial pressure, r.f. power, substrate temperature, distance between a substrate and a target, etc. COSCOS can also control the crystal preferred orientation of coatings which strongly affect those frictional property. Platinum oxide and palladium oxide coatings were synthesized by COSCOS, then the crystal structure was analyzed with X-ray diffraction spectroscopy and frictional properties of the coatings were measured by a tribometer at an atmospheric pressure.     

Composite platinum group metals: A new structural material for glass handling equipment and laboratory apparatus

The cost of platinum and platinum-rich alloys inevitably leads to attempts to find cheaper alternative materials, particularly for applications where they are used for structural purposes. Previous work has generally been centred on coating base metals with platinum or on the development of palladium-rich alloys. However, both of these approaches have limitations particularly with regard to strength, corrosion resistance and reliability. The application of zirconia grain stablised technology to this problem has now resulted in the production of a composite trimetallic material, designated ZGS Platinum “TriM”. This largely overcomes the problems associated with earlier materials and dramatically reduces material costs.     

等离子喷涂与溶胶-凝胶法组合制备中高温太阳能选择性吸收复合涂层

为了制备出高效的非真空、中高温太阳能选择性吸收涂层,先在光亮Cu片上等离子喷涂Cr—Al2O3金属陶瓷吸收层,再用溶胶-凝胶法在其上制备了SnO2选择性透过膜,对复合涂层的相结构、表面形貌、光学性能进行了研究。结果表明：金属陶瓷吸收层由金属颗粒Cr与Al2O3组成,物相稳定,表面凹凸不平,气孔较多,发射率较高;覆盖Sn...     

Correlation of processing technique and microstructure of platinum aluminide bond coats with performance of thermal barrier coatings deposited on nickel base superalloy

Abstract

We show that the performance of thermal barrier coating systems is critically dependent upon the processing technique and microstructure of platinum aluminides utilised as bond coats. It is demonstrated by thermal exposure tests at 1150°C in air with 24 h cycling period to room temperature that the average useful life of a coating system employing zirconia–7 wt-% yttria as top coat and alloy MAR M002DS as substrate is increased from 192 to 480 h by replacing a three-layer bond coat aluminised by conventional pack cementation with a two-layer bond coat aluminised by chemical vapour deposition. Before each aluminising process, the superalloy has been electroplated with a platinum layer about 7 μm in thickness. Microstructural characterisation using scanning electron microscopy combined with energy dispersive X-ray spectroscopy, electron-probe microanalysis, transmission electron microscopy and X-ray diffraction indicates that the superior performance provided by the two-layer bond coat is related to its higher thermal stability enhancing the adhesion of the thermally grown oxide. However, both coating systems are found to fail by the same mechanism involving loss of adhesion between the thermally grown oxide and bond coat.     

Optical second harmonic generation at platinum phthalocyanine-modified platinum electrodes

Optical second harmonic generation (SHG) has been used to observe changes within electronically conducting platinum phthalocyanine (PtPc) films deposited on polycrystalline platinum electrodes as the film undergoes electrochemical modification. PtPc-modified electrodes produced enhanced SHG responses over bare platinum surfaces. This is proposed to be due to an electric quadrupole contribution from the PtPc molecule. Examination of the polarization dependence of the SHG response reveals that electroactive PtPc molecules exist in environments both parallel and perpendicular to the electrode surface. It has been possible to observe redox processes occurring within the films by monitoring the magnitude of the SHG response with variations in potential. The decrease in SHG signal has been shown empirically to be proportional to the charge removed from the film during oxidation of the phthalocyanine (Pc) ring.     

能量色散X射线荧光光谱法测定铂钌合金中的铂含量

应用能量色散X射线荧光光谱法（EDXRF）对铂钌合金（铂含量为90％～96％）中铂含量进行测定。利用一套铂钌为主量的工作标样,测量并收集此工作标样所含元素的特征X射线光谱,建立标准工作曲线,编制和优化分析程序,测定铂钌合金中铂元素的含量。对铂钌合金样品的测试结果与其他方法进行比较,证明方法可行。铂钉合金中铂含量在90％-96％时,分析精度优于0．3％。     

Effect of platinum oxidation on the characteristics of standard platinum resistance thermometers

Platinum oxidation in PTS-10 and PTS-25 standard platinum resistance thermometers has been studied. The experimental results show that heat treatment of a thermometer at 100–300°C can increase its resistance at the triple point of water by the equivalent of 1.5 mK. A procedure for calibration in the range 0–450°C is recommended. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 41–44, July, 1996.     

Multiple platinum printing

Abstract

In the development of platinum printing as an art, one of the most encouraging signs of its individuality and virility has been the latitude of the hand-coated platinum print.     

High speed friction and wear characteristics of vapor- deposited coatings of titanium carbide and tungsten carbide plus cobalt in a vacuum environment

Instrument-size gas-bearing applications frequently require hard wear- resistant coatings on lightweight thermally conductive substrates. Titanium carbide and tungsten carbide coatings approximately 1–2 μm thick were prepared for this purpose on both beryllium and beryllium oxide substrates by sputter deposition. Titanium carbide coatings approximately 50 μm thick were also prepared using activated reactive evaporation techniques. Test fixturing was developed using a vertical-axis turbomolecular vacuum pump to provide both a vacuum atmosphere and a high speed spindle for specimen motion. Coated specimens having beryllium substrates were mounted directly on the pump spindle, while specimens with beryllium oxide substrates were brought into contact with the rotating member at a specified load for a given length of time. Specimen contact was made at a sliding velocity of approximately 7.0 × 10³ cm s^-1 in a vacuum pressure of less than 5.0 × 10^-6 Torr. Specimen surfaces were completely characterized before and after testing using surface profilometery, light microscopy and scanning electron microscopy with X-ray analysis and X-ray diffraction techniques.     

2-Methoxycycloocta-1,5-dienyl platinum complexes as precursors for platinum nanoparticles

Thermolysis of [Pt₂(μ-OR)₂(C₈H1₂OMe)₂] (R = Me or Ac) in hexadecylamine (HDA) at 210°C under argon atmosphere gave platinum nanoparticles which were characterized by XRD, EDAX and TEM analysis. Both spherical (∼ 10 nm) and rod-like (∼ 19 nm length with aspect ratio of 2·3) face centred cubic (fcc) platinum metal nanoparticles could be isolated. The thermogravimetric analyses of these complexes revealed that they undergo a single step decomposition leading to the formation of platinum metal powder.