Three YSZ powders with different particle size distributions and an ethanol-based YSZ suspension were deposited on steel substrates using a cascaded plasma torch with a 9 mm nozzle. Coatings with dense, porous, segmented, and columnar microstructures were achieved by varying process parameters such as gun current, argon flow rate, spray distance, and suspension injection pressure. Linear relationships between in-flight particle state and process variables were observed and are shown to correlate well with coating structure and porosity.

Wear and corrosion protection are the main applications for carbide cermet coatings which are most commonly applied by HVOF in the field of thermal spray technology. The TriplexPro-200 offers to produce carbide coatings economically and at an outstanding quality level. The influence of spray parameters, material composition and morphology was investigated and put into comparison to the established HVOF process. Two spray parameters for the TriplexPro-200 were used: standard setup in which the particle velocities around 200 – 280 m/s and the high-velocity setup reaching particle velocities above 550 m/s. Materials with different morphologies were tested showing influences on coating structure and residual stress. The material compositions are WC-Co and WC-CoCr as they are widely used in wear and corrosion resistance. Coatings sprayed with the standard setup of the TriplexPro-200 show coating qualities beyond single cathode APS systems and at higher deposition efficiency and feed rate. In the high velocity operation window the coatings become HVOF-like with hardness values up to 1200 HV 0.3 and very low porosity level. The measurement of the residual stress shows that compressive stress can be achieved using the TriplexPro- 200 technology.

This paper focuses on the use of hydrogen and nitrogen as secondary gases for atmospheric plasma spray using the TriplexPro-210 gun platform. The paper includes process mapping of particle state in addition to measurements of actual stress states within the coating during coating application. The feedstock powders used for this investigation include yttria stabilized zirconia, chromium oxide, nickel chromium aluminum and nickel aluminum. In addition, the paper discusses differences in application costs.

Triplex is a second generation plasma gun technology that offers multiple benefits in term of rates of application and deposit efficiencies. This paper focuses on Triplex technology as it relates to daily operational aspects of a typical thermal spray facility. Today, Triplex is the only plasma technology that features "fixed" parameter operation for extended run times which has significant impact at multiple levels within the spray shop. Data presented will compare Triplex to first generation plasma technology with regards to quality, training, simplification, and process repeatability.

Sensor technology is becoming more of a production tool to help improve production quality, reliability and reduce manufacturing costs. Combustion sprayed abradable seal products are a family of materials where this technology will be helpful to the applicator and end user. Although these materials have been used for over forty years with wide success in the aerospace and industrial gas turbine industries they can be sensitive to spray process variables. Changes in spray processing conditions during spraying will change the desired microstructure and coating properties. This paper looks at a commercially available combustion powder and how process parameters such as gas flows and powder feed rates affect output process variables such as particle velocity and temperature. This paper will also discuss the importance of understanding the influences that particle temperature and velocity have on coating properties such as hardness, erosion and coating strength. Deposit efficiency of these combustion powders is also measured as a function of particle temperature and velocity. Based on particle temperature and velocity, sensor diagnostic tools can provide warnings about process changes resulting in fast corrective action. The benefits of this sensor technology are the potential for less inspection requirements, improved microstructure control, reduced in-service failures, and less time and labour required for stripping coated components that may not meet specification standards.

The influence of secondary hydrogen and current on the deposition efficiency (DE) and microstructure properties of yttria-stabilized zirconia (YSZ) coatings was evaluated. In order to better understand the influence of the spray process on coating consistency, an YSZ powder, -125+44 µm, was sprayed with nitrogen/hydrogen parameters and a 9MB gun. DE and coating porosity produced using two different spray gun conditions yielding the same input power were compared. Amperage was allowed to vary between 500 A and 560 A and hydrogen was adjusted in order to maintain constant power, while nitrogen flow was kept at a fixed level. Several power conditions, ranging from 32 to 39 kW, were tested. Different injection geometries, i.e., radial with and without a backward component, were also compared. The latter was found to produce higher in-flight temperatures due to a longer residence time of the powder particles in the hotter portion of the plasma. Porosity was based on cross-sectional photomicrographs. In-flight particle temperature and velocity measurements were also carried out with the DPV-2000 for each condition. Test results showed that DE and coating density could vary significantly when a different hydrogen flow rate was used in order to maintain constant input power. On the other hand, DE was found to correlate very well with the temperature of the in-flight particles. Therefore, to obtain more consistent and reproducible DE and microstructures, it is preferable to maintain constant the in-flight particle temperature instead of keeping the input power constant by adjusting the secondary hydrogen flow rate for obtaining more consistent and reproducible DE and microstructures.

Two 7-8 wt% yttria-stabilized zirconia powders of similar size and chemistry but having different microstructure properties and manufacturing routes were studied. One significant difference was the density and internal porosity of the starting powders. Deposition efficiency (DE) of the low density (LD) powder was found to be higher and less sensitive to changes in the spray process parameters than the high density (HD) powder. Probing the in-flight particle characteristics with the DPV- 2000 made it possible to link the observed DE values with the in-flight particle temperature. For each powder, DE was found to depend mainly on a single variable, the in-flight particle temperature. DE was found to vary strongly with particle temperature for temperatures under 2700°C, whereas the dependence with particle temperature was much less important above 2700°C. Variations in DE seemed to evolve according to variations of the melted fraction of the sprayed material. Since the LD powder was found to achieve higher particle temperatures at given spray conditions, DE was found to be higher for the LD material and the range of variations in DE was found to be much less than that observed with the HD material. Examination of the coating microstructures revealed that a coating produced with the LD powder had slightly higher porosity than that produced with the HD powder at similar inflight parameters. Spraying at higher in-flight particle temperature or velocity, which resulted in higher and more robust DE values, tended to yield coatings with lower porosity, resulting in coating density exceeding the tolerance range specified by some end-users. Increasing the powder feed rate and using conditions that produced a higher in-flight particle temperature were found to increase the porosity up to an acceptable level without significantly degrading DE. Therefore, a solution was found that not only reduced the sensitivity of DE to changes in the spraying conditions but also increased the rate of production by reducing the time required to spray the part.

Atmospheric plasma sprayed thermal barrier coatings have been used for years in manufacturing as well as revision and repair. This paper provides an overview of recent advancements in TBC technology and discusses the factors with the greatest impact on coating life, reliability, and performance. Paper includes a German-language abstract.