Wear and corrosion of aircraft actuator parts and helicopter gearbox rotating shafts and also wear of seals working against these parts can lead to oil leaks, which require expensive maintenance and increase the risk of failure. The Hardide nanostructured Chemical Vapor Deposition (CVD) Tungsten Carbide coating can help reduce oil leakage from gearboxes and actuators and increase maintenance intervals. The coating protects metal pistons and shafts from abrasion and corrosion, keeping their surface roughness parameters within optimum ranges for longer; this reduces seal wear and makes the whole unit more durable and reliable. The 50-100 microns thick CVD Hardide coating can be applied uniformly on internal and external surfaces and has enhanced fatigue and anti-galling properties. The coating has enhanced wear resistance outperforming Hard Chrome by 14 times and Thermal Spray WC-Co (12%) by 3 times. The fine-grain coating nanostructure wears uniformly so even worn Hardide coating shows no hard micro-grain asperities which are abrasive for seals. The coating is free from porosity and from Cobalt binder and is an excellent barrier against corrosion. As a result the coating keeps the optimal seal-friendly surface finish for longer even in abrasive and corrosive environments. The coating was qualified by Airbus as an environmentally-friendly replacement for Hard Chrome plating.

In this research project a hybrid technology is developed to repair turbine blades. This technology incorporates procedural and manufacturing aspects like raising the degree of automation or lowering the effort of machining and includes materials mechanisms (e.g. diffusion processes) as well. Taking into account these aspects it is possible to shorten the process chain for regenerating turbine blades. In this study the turbine blades of the high pressure turbine are considered and therefore nickel-based alloys are regarded. To repair or regenerate turbine blades the following methods are employed: welding and brazing and a subsequent aluminizing CVD-process. The focus in this work lies on the brazing method and the required filler-metal is applied together with the hot-gas corrosion protective coating by means of thermal spraying and represents the first stage of this hybrid technology. In the second stage of this hybrid technology the brazing process is integrated into the aluminizing CVD-process and a first effort is presented here.

In the oil industry, logging systems involving geological sensors are designed to operate under increasing severe service conditions of deep and horizontal boreholes. Under these conditions, metal matrix composites (MMCs) with ceramic reinforcement are applied on components to achieve wear and corrosion resistant systems. The ‘cold spray’ could be described as a cold and inert process to form coating layers through severe plastic deformation of a ductile metal. Ceramic/metal MMC coating could be achieved by co-deposition of a ceramic with a ductile material. In this work, it was it was investigated the use of MMC B 4 C-Ni coating from both mechanically milled blends or B 4 CNi CVD coated batches. Powder blends involving Ni powder with fine or coarse B 4 C powders were prepared by mechanical milling. Three CVD coated B 4 C-Ni powder batches were synthesized with 30, 40 and 50 Ni wt% respectively. Cold spray coatings were achieved with 1 pass and 5 passes to investigate the building-up mechanisms and interfaces with AISI316L. Powders and cold sprayed coatings microstructures were observed by optical and scanning electron microscopies and further quantitative image analysis were carried out to determine the content of B 4 C embedded in the Ni matrix of B 4 C-Ni cold spray coatings. The highest B 4 C vol.%, up to 45%, could be reached in the case of B 4 C-Ni coated powder. Micro-hardness values of such MMC coatings were also determined through Vickers micro-indentation. The beneficial role of the Ni surrounding layer on coating formation is discussed in relation to the unique features of the microstructures obtained by cold spray of B 4 C-Ni coated powders.

Recent developments in hybrid low pressure thermal spray technologies such as Plasma Spray-Thin Film (PS-TF), PS-PVD, PS-CVD are being increasingly used to develop functional inorganic coatings and films for emerging high end energy applications. The requirements of such coatings and films are more highly specified than those of conventional plasma spray coatings. Successful film deposition therefore requires not only the development and application of novel operating parameters, but also goes hand-in-hand with tailored feedstock materials development. Targeted development by Sulzer Metco has allowed applications to evolve into fields where conventionally competitive manufacturing technologies would be applied; potentially enabling entirely new fields of plasma spray manufacturing to emerge. Such applications include corrosion protection and electrolytic films in SOFC, gas tight mixed electron and ion conducting membranes for gas separation and thin, transparent functional layers in photo-voltaic applications. This paper provides a brief overview of the status of developments of several high end emerging energy applications which are being developed using such hybrid low pressure plasma spray technologies.

This paper provides an overview of chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes and the advantages they offer physical vapor deposition for the application of friction and wear coatings for micromechanical assemblies and components. It explains how hard and solid lubricant phases can be applied by these non-line-of-sight deposition methods, achieving nanoscale conformality and coating uniformity on buried surfaces and interfaces. It also discusses inherent disadvantages and explains how plasma excitation can be incorporated in either process to overcome material limitations.

The LARGE is a new generation DC-plasma torch featuring an extended arc which is operated with a perpendicular gas flow to create a wide (up to 45 cm) plasma jet well suited for large area plasma processing. Using plasma diagnostic systems like high speed imaging, enthalpy probe, emission spectroscopy and tomography the LARGE produced plasma jet characteristics have been measured and sources of instability have been identified. With a simple model/simulation of the system LARGE III-150 and numerous experimental results, a new nozzle configuration and geometry (LARGE IV-150) has been designed, which produces a more homogenous plasma jet. These improvements enable the standard applications of the LARGE plasma torch (CVD coating process and surface activation process) to operate with higher efficiency.

The aim of this study is to develop for thermal barrier applications a new process in which coatings exhibit properties between those of APS and EBPVD. This process includes two conventional D.C. plasma torches working in a chamber whose pressure can vary between 30 and 100 kPa. Micro-sized yttria stabilized zirconia powders are injected in both plasma jets to vaporize them, at least partially, and produce finely-structured coatings from vapor and micro-droplets deposition. The torch arrangement allows separating the vapor and the very small particles (less than 1 µm) from the partially vaporized bigger ones. The diagnostics are based on optical emission spectroscopy, pyrometry, imaging of particles trajectories and coating microstructural characterization.

Since Dye sensitized solar cell (DSC) is a solar cell which uses anatase film as photo voltaic device, production cost of DSC can be very low in comparison with that of silicon solar cell. Besides, according to some theoretical discussion on DSC, the electric power conversion efficiency can be raised to 30%. Therefore, DSC will be mainly used in future. In this study, in order to develop a low cost fabrication process for photo voltaic device of DSC, photo-catalytic titanium oxide film depositions were carried out by thermal plasma CVD (TPCVD) and thermal spraying. As working gas for plasma jet, and substrate, Ar gas and 20mm×40mm×1mm copper plate were used. Feedstock materials were titanium tetra butoxide in TPCVD and rutile powder in thermal spraying. In the DSCs using these films, cathodes (titanium oxide coated electrodes) were located beneath the transparent anodes. Consequently, in the case of TPCVD, anatase dominant film could be deposited and the DSC using this TPCVD film could generate 50 mV in electro motive force. Furthermore, even in case of thermal spraying, though rutile powder was used, photo-catalytic coating (anatase and rutile mixture coating) could be obtained by cooling substrate during coating and post heat treatment. It was confirmed that the electromotive force of the DSC using this thermal spray coating was almost the same as that of the DSC using the TPCVD film. From these results, these thermal plasma processes was found to have high potential for DSC fabrication.

It is difficult for engineers and scientists to remain up to date on the wide variety of surface engineering technologies available for product and process design, to solve maintenance problems, etc. This paper provides a brief overview of several of the major types of surface processes and resulting coatings or other surface treatments. It is intended only to provide an elementary introduction to serve as a background for further inquiry by the reader or to assist those not familiar with a given field to more easily understand other presentations in this conference session. The technologies considered include thermal spray, physical vapor deposition, and chemical vapor deposition.

In the hypersonic plasma particle deposition process, vapor phase reactants are injected into a plasma and rapidly quenched in a supersonic nozzle, leading to nucleation of nanosize particles. These particles impact a substrate at high velocity, forming a coating with grain sizes of 10 to 40 nm. As previously reported, coatings of a variety of materials have been obtained, including silicon, silicon carbide, titanium carbide and nitride, and composites of these, all deposited at very high rates. Recent studies have shown that slight modifications of the process can result in nanosize structures consisting of single crystal silicon nanowires covered with nanoparticles. These nanowires are believed to grow in a vapor deposition process, catalyzed by the presence of titanium in the underlying nanoparticle film. However, simultaneously nanoparticles are nucleated in the nozzle and deposited on the nanowires, leading to structures that are the result of a plasma CVD process combined with a nanoparticle spray process. The combination of these two process paths opens new dimensions in nanophase materials processing.

In order to develop a functional film deposition process with high deposition rate, as a basic study, deposition of zinc oxide film by thermal plasma CVD (TPCVD) in the air was carried out. As ingredient, working gas and substrate, ethanol diluted zinc acetate solution, Ar and 430 stainless steel were used. As for deposition condition, Ar gas flow rate was fixed at 20SLM, deposition distance (distance between substrate surface and nozzle outlet of plasma torch) was varied 50 to 200 mm, zinc acetate concentration in the ingredient was varied 20 to 50 vol%, and ingredient feed rate was varied 30 to 200 ml/h. Consequently, with varying deposition distance, not only crystallized film but also amorphous film could be deposited. In the case of crystallized film, photo-catalytic properties could be confirmed in the films by methylene blue decoloration testing and wettability testing. Besides, in this case, film structure could be changed from lamellar to columnar by decreasing zinc acetate/ ethanol ratio. From these results, this process was found to have high potential for high rate functional film deposition process conducted in the air.

Coating technology is progressing at a steady rate with continuous significant improvements in the coatings performance. In the aerospace field, as well as in the stationary gas turbine field, coatings deposited by different processes (thermal spray, CVD, EBPVD) play an important role in order to increase the performances of the engines. In particular, in order to improve the resistance to oxidation and corrosion at high temperature, aluminium is deposited by several techniques (pack aluminising, above the pack and CVD) in alternative or addition to thermal spray coatings (mainly MCrAlY alloys where M stands for Co, Ni or CoNi). These MCrAlY coatings are generally deposited by Low Pressure Plasma Spray (LPPS) or Vacuum Plasma Spray (VPS), but also by High Velocity Oxygen Fuel (HVOF) and Air Plasma Spray (APS). This paper addresses the study of aluminium coatings deposited by CVD on CoNiCrAlY bond coats deposited by different processes: VPS with F4 gun, LPPS with EPI gun and HVOF. The aim is to verify if and how the different CoNiCrAlY coatings obtained by these three processes with different content of oxides and porosity could affect the deposition rate and quality of the Al coatings. The obtained samples have been characterized from the metallographic point of view in order to determine porosity, thickness and structure of both CoNiCrAlY and Al coatings. Al coating thickness has been taken as parameter in order to define the Al coating deposition rate on the three different CoNiCrAlY coatings. Further tests for the determination of aluminium content and chemical composition of the coatings are in progress.

Thermal plasma CVD is hoped to be made fit for practical use because this process is the process which can fabricate precisely structure and component controlled coatings. Especially, TPCVD will be used in the industrial fields where thermal spraying has been used so far since TPCVD come to be studied under an atmospheric environment recently. However, TPCVD coatings fabricated under an atmospheric environment is porous and brittle. So that, TPCVD has been mostly carried out under a low pressure environment and high equipment cost has been demanded. As for the method to solve this problem, according to the report on a gas-deposition process, improvement of the jet flow is thought to be useful. Therefore, in this study, in order to obtain dense and rigid film by TPCVD under an atmospheric environment, Dense oxide coating deposition by High velocity TPCVD utilizing boiling of metal alkoxide was carried out. Consequently, though only brittle coating was deposited on the condition without boiling of metal alkoxide, dense and rigid coating was deposited even under an atmospheric environment on the condition with boiling. From this result, TPCVD was found to have high potential for rapid deposition of dense and rigid coatings.

The system B-C-N contains the hardest known materials like diamond, cubic boron nitride and boron carbide, which also show excellent chemical resistance. The oxidation resistance is shifted to higher temperatures in comparison to pure diamond. But pure BCN coatings cannot be produced by conventional thermal spray processes, as the materials lack both a liquid phase and sufficient ductility to permit deposition. Conventional VPS equipment is successfully applied in Thermal Plasmajet CVD processes for high deposition rate synthesis of diamond coatings. The feasibility of SiCN or boron carbide synthesis by this method has also been proven. The use of liquid precursors results in outstanding deposition rates and improved operational safety. Methylized borazine is applied for synthesis of BCN coatings in thermal plasma jets. The use of single source precursors is advantageous with concern to the homogeneity of the coating forming species stoichiometry. For long-term storage cooling is necessary, but also under ambient conditions the precursor shows sufficient stability. Plasma gun nozzles with different diameter and design are applied and evaluated with concern to the resulting coating properties. Deposition rates of up to 1,500 µm/h have been achieved with homogeneous coating thickness and morphology on areas with 50 mm diameter. No porosity is detected in SEM investigations on cross sections and fracture surfaces show a fine columnar coating morphology. XRD investigations point at an amorphous structure. Only for very high substrate temperatures the formation of crystalline boron carbide B8C and h-BN or graphite phases is detected. Oxygen contamination results in boric acid formation and therefore has to be avoided carefully. During coating deposition on mild steel substrates the formation of boride and nitride reaction zones is observed. VPS sprayed nickel or molybdenum interlayers permit to inhibit the evolution of reaction zones. Thereby BCN coatings with thicknesses of up to 10 µm are deposited without local delamination. Space resolved emission spectroscopic analyses are carried out in order to detect coating forming and intermediate species. As Thermal Plasmajet CVD is a pure gas phase deposition process, the control of the space resolved emission permits easy process control.

Study of the injection of liquid sprays into thermal plasmas has a number of important applications. Examples include Thermal Plasma Chemical Vapor Deposition (TPCVD), hazardous waste destruction and, ICP atomic emission or mass spectrometry in analytical chemistry. The spray is comprised of thousands of single liquid droplets. To calculate the mass, momentum and energy exchange between the gas and the spray, one must account for a distribution of droplet sizes, velocities, and temperatures. For some cases, droplet collision and breakup also are important. This paper developed a model for the transport and evaporation of liquid droplets sprayed into an radio frequency inductively coupled plasma (rf-ICP). The model considers the evolution of spray distribution function as the liquid spray travels through the discharge. Coupling calculations between plasma gas and water spray is performed for a typical rf-ICP torch. This model is capable of predicting the thermal and dynamic behavior of the liquid spray and its effects on the plasma gas for different rf-ICP operating conditions.

This work evaluates the microstructure and composition of zirconia films produced by thermal plasma chemical vapor deposition (TPCVD). The results show that TPCVD has the potential to produce durable ceramic films with columnar structure, even in open air. Paper includes a German-language abstract.

This paper investigates the potential of radio frequency thermal plasma chemical vapor deposition for producing Sr-doped La-Mn-perovskite and yttria-doped zirconia layers for solid-oxide fuel cells. Aqueous solutions were used as starting materials and were injected into the hot plasma core by means of an air-assist atomizer. Test results show how the microstructure, dopant distribution, and phase purity of the resulting layers depends both on process conditions and the material system. Paper includes a German-language abstract.

Materials in the system Si-C-N feature excellent properties for wear and corrosion protection applications even at elevated temperatures and an excellent thermal shock resistance among the ceramics. As these materials have no melting point, they cannot be processed purely by conventional spraying techinques, but need to be synthesized. Plasmajet CVD processes with single and triple DC torches and HF torches with supersonic nozzles have successfully been applied to produce Si-C(-N) coatings on different steel, aluminum, titanium and copper alloys as well as on graphite. Various liquid single precursors with suitable structure have been tested and evaluated with regard to the morphology and structure of the produced coatings. The processes are compared taking into account their characteristics concerning the injection modes, gas temperature and velocity profiles. Emission spectroscopy is used to determine the mechanisms of the coating formation. Guidelines for the optimum production of Si-C(-N) coatings by Plasmajet CVD are deducted.

Thick alumina coatings produced by Air Plasma Spraying have an interconnected porosity, thus the use of these coatings in oxidizing or corrosive environment is not suitable. In this paper, a study is developed in order to limit this problem on metallic substrates. It consists in using two successive techniques: APS and PECVD. Two parameters have been shown to be important: the roughness and the preheating temperature. Two types of duplex (PECVD coating as top coat or as bond coat) have been achieved on two substrates (TA6V and stainless steel 316L). The optimization of each process has shown that the substrate has to be grit blasted and preheated (360°C for PECVD and 250°C for APS). This study has revealed that a good (36 ± 5 MPa) APS coating adhesion was obtained on smooth TA6V substrates (due probably to a chemical reaction between TiO 2 and alumina) while for stainless steel substrates, the Ra has to be at least 2µm to achieve 66 ± 5. When observing the first APS splats sprayed on the PECVD alumina smooth layer, they exhibited a specific appearance: low flattening degree (about 2 against 5 on metallic substrates) with most of the alumina in the splat rim or some sort of lace morphology. However, as a whole, the adhesion of the APS coating on the PECVD one was excellent: 60 + 4. An electrochemical method has shown that the PECVD layer on APS coating has reduced drastically its open porosity.

In mechanical engineering there is an increasing demand for lightweight design and materials engineering from the view points of weight reduction, reduction of consumed energy and upgrading of performance. One major drawback of light metal alloys is their poor tribological properties concerning friction and wear under high surface loadings. This study focuses on the development of combined coatings on light metal substrates which show high wear resistance and low friction coefficients under dry sliding conditions. The combined coatings consist of a thermally sprayed ceramic or metallurgical primary coating to provide the wear resistance. Subsequently a coating with dry lubricating ability is deposited to achieve a low friction coefficient, either by application of a lubricant lacquer containing microscale solid lubricant particles (e.g. PTFE, MoS 2 ), by cathode sputtering of MoS 2 or by deposition of pure carbon containing coatings (a-C:H) by plasma assisted CVD.