Industrial demands for higher quality, yet lower cost thermal spray coatings have driven the development of highly automated and fully integrated thermal spray systems. These systems include computer control of the powder, gas, electrical power, and cooling fed to the spray device, auxiliary cooling of the part, and motion of the part spray device. The subsystems may include closed-loop control of particular parameters such as the powder feed rate. More fundamental closed-loop or "intelligent" processing systems are under development. A key element in such systems is the ability to sense critical parameters that are indicative of the coating's properties in such a manner that changes in the process can be made to maintain its properties while the coating is being deposited. For example, it is widely recognized that the temperature, velocity, and size distribution of the powder particles during flight are largely responsible for the properties of the resultant coating. A variety of sensor systems have been developed recently that can measure one or more of these properties. At least one such system is capable of measuring all three parameters for the full cross section of the spray. Computer controls, closed loop systems, and intelligent processing cannot compensate for poorly designed, manufactured, or maintained equipment. Nor can they compensate for unsatisfactory preparation of the surface, feedstock (powder, gas, power), finishing equipment or materials, or training of operators. Sufficient attention to all of these factors may even make the investment in some more sophisticated systems questionable for some applications. This paper will attempt to provide an overview of the currently available highly automated and integrated thermal spray systems used for intelligent processing and consider some criteria for its selection and use.

The plasma spray technology has shown a considerably evolution during the last 10 years. Modeling and diagnostic methods also have shown a strong development and offer tools for a better characterization and simulation of the plasma spray processes. In the same time some new types of plasma torches were developed. The motivation for the development primarily was the productivity measured in spray rate and deposition efficiency. However the necessary level of energy used for the melting and the accelerating of the powder was not always considered as important factor. In the future this factor certainly will take more importance. The reliability of the process becomes to be considered as a major aspect. During the last decade two directions of development were taken. One direction is the axial injection of the powder in the plasma jet. This process allows an excellent control of particles trajectories and looks as attractive process, however the stability of the arc root is not really realized through the axial injection. The stability of plasma spray process can be increased using the principle of cascaded anode to fix the arc root and provide quasi constant condition for the melting and accelerating of the injected powder. The current density of the cathode plays an important roll regarding the time life and also the stability of the process. It was realized an improvement of a factor 5 to 10 of time life of cathode by the using a multi cathode plasma torch with low current density. This technology shows a significantly improvement by the deposition of metallic alloys and ceramic regarding the productivity and the constant quality level of the coating.

An important aspect in the successful commercialisation of thermal spray processing is a safe and cost efficient gas supply system. As coating techniques such as High Velocity Oxygen Fuel spraying, (HVOF) High Pressure Plasma spraying (HPPS), High Pressure High Velocity Oxygen Fuel kerosene based systems (HPHVOF) and the recent developments in Cold Gas Dynamic spraying become more prominent, so the requirements on existing standard gas delivery systems designed for less demanding applications such as flame and plasma spraying need to be up-rated and improved. This work highlights recent developments in gas safety supply equipment dedicated to the thermal spray sector, the use of gas detectors in thermal spray workshops, more cost efficient gas delivery systems for fuel gases such as hydrogen, LPG propane, propylene and acetylene, and also covers improvements in gas delivery systems for the process gases such as oxygen, nitrogen and argon. The paper looks at various gas supply options, comparing compressed gas cylinders, liquid gas cylinders and bulk liquid supply vessels outlining the benefits and limitations of each systems in relation to the individual spray techniques. The higher pressures and flow rate associated with the growth of kerosene based fuel guns has resulted in an increased demand on the conventional compressed oxygen supply systems making them less cost effective and unworkable in a production environment. The paper covers new liquid oxygen supply cylinders and novel bulk tank systems that reduce cylinder holdings while reducing gas wastage due to lack of pressure. With the increase in higher thermal energy systems, necessity to more closely control the temperature of sprayed the component has outstretched the demands on conventional compressed air cooling systems. In the past, the use of cryogenic cooling gases such as carbon dioxide has been restricted by increased cost. However it has been shown in a number of cases that often the hidden costs of running air compressors, including the use of moisture traps, and oil filters can be greater than using clean, high purity cryogenic liquid gases such as carbon dioxide and nitrogen. The paper outlines the details of such cooling systems. The commercial success of Cold Gas Dynamic spraying may in future rely on a cost efficient, high pressure and high volume gas delivery systems for either helium or nitrogen. The paper describes a novel high pressure supply system presently used in another application suitable for Cold Gas Dynamic spraying with nitrogen able to generate pressure in-excess of 30 bar and flow rates above 120m3/hr from a liquid vessel.

Being able to offer a consistently high level of spray coatings on a global scale has become more and more the trend in thermal spraying. For this reason it is extremely important that auxiliary materials such as industrial gases or spray materials of a high quality are provided world-wide. In connection with their respective applications, industrial gases must always be available at a specified purity level. In order to ensure such a purity, industrial gas producers invest a great deal of time and energy in analysis and supply concepts which guarantee this purity from the tank or cylinder through to the transfer point. This paper will provide an overview of state-of-the-art supply and purity concepts, as seen by the gas industry, and the influence of fluctuating gas quality. Examples will also be given for the differing gas qualities in individual countries.

The plasma spray process is one of the oldest and most useful thermal spray processes used in industry today. The principles of plasma spray are complex. The many factors that affect plasma spray make understanding and manipulating the process a difficult task. Although it is impossible to isolate each of those factors, the understanding of the way they affect the quality of the coating can help the sprayer make an improved judgement for coating development and application. This paper is an attempt to identify the various factors, including plasma spray equipment configurations, plasma gases, feedstock and manipulation, and discuss their effect on a particular plasma spray coating application from a job shop perspective. Also, plasma spray coating applications are discussed.

This article investigates composite powder materials based on double chromium and titanium carbides with nickel-chromium binder produced using self-propagating high-temperature synthesis. It focuses on the hypersonic velocity oxygen fuel coatings from the synthesized powders. Laboratory tests were focused on the solid particle erosion which occur in energy production systems such as fluidized bed combustors, advanced pulverized cool boilers, and entrained coal gasifiers. Tests were conducted at elevated temperature in a blast nozzle type of tester using bed or fly ashes retrieved from the operating CFB boilers. It was observed that, when adjusting carbide phase composition and chromium content in titanium carbide solid solution, one can control the oxidation kinetic and wear resistance of the material. Fine-grained structure and high cohesion strength of the composite materials formed during synthesis provide their excellent elevated temperature erosion performance in a wide range of test conditions.

The authors carried out in 1999 a multiclient market research covering the Thermal Coatings business in Europe. This work has allowed to obtain detailed business facts relative to the industry and has provided an in-depth understanding of applications, markets, competition, key factors for success and industry structure. Thermal coatings are defined here as coating parts by hardfacing (e.g. MIG, TIG, PTA, laser...) or thermal spray (flame, arc, plasma, HVOF...). This study also provided a further opportunity to investigate about present business issues and to provide a fresh look into growth opportunities. This presentation intends to provide the scientific community with a summary of this business analysis and to stress business issues and factors found to constrain business growth today. We do expect that a more carefully focused teamwork between independent R&D and the supply chain could significantly accelerate the growth of the Thermal Coatings business in the future.