Coating Processes Technology Advancement
Monday, April 10, 2000 1:30 PM in Room Royal Palm Salon 1-3
A4-2-1 Optimization of Plasma-sprayed Coatings by Thermography
G. Zenzinger (München GmbH, Germany)
Thermography is a noncontact integral technique for temperature measurement and for representation of temperature differences in thermal images. The use of thermography in NDT and process control increased rapidly when high-performance infrared cameras appeared in the market place. Thermographic systems of high geometric, thermal and time resolutions (e.g. 0.02 K at a video frequency of 120 Hz) have recently become available. Pulse thermography, commonly used in thermal NDT, is a powerful technique for the nondestructive evaluation of thermal barriers, such as ceramic plasma-sprayed coatings. Pulse thermography is applied to detect delaminations and cracks but also to measure coating thicknesses and thermal properties or porosity. In the production line infrared pyrometry is a suitable tool for process control and optimization by monitoring the surface temperatures during plasma spraying. A dual sensor system with an infrared probe and a triangulation sensor for on-line coating temperature and thickness measurement was built and tested in the productione line. The results show the economic and technical potential of on-line contactless measurement techniques for the optimization and stabilization of plasma-spraying processes.
A4-2-3 Six Sigma for the Advancement of Coating Technology
T.R. Grossman (GE Aircraft Engines)
GE Aircraft Engines has undertaken an aggressive effort to use the tools and methodoligies of Six Sigma in all of our business practices and manufacturing processes. These tools are especially useful in developing, evaluating and maintaining the complex processes used to make coatings. This paper discusses how the Six Sigma tools are being used on a daily basis to ensure that GE Aircraft Engine coatings meet both design requirements and customer expectations.
A4-2-4 The Impact Potential of the Inline EB=PVD Concept to Repair Coating Production
W. Beele, A. van Lieshout, P. van Neerven, G. Marijnissen (Interturbine Coating Center, The Netherlands)
The inline EB-PVD coater is a new production philosophy to meet the increasing demands for cost efficient productivity and quality assurance in EB-PVD gas turbine coating applications. Both requirements are being met by the unique design of this machine@paragraph@The EB-PVD production system design with their 2 or 4 chamber load-lock/sting principle is compared to the inline design, specifically with respect to its conceptional differences with small batch configurations. The modularity of the system and the trolley concept is providing the flexibility, as it is required specifically in the repair market. The repair market requires optimum Turn-Around-Times and a high flexibility in terms of the varying amount of components per repair job.@paragraph@The paper will review why the complete disconnection of the trolley between the completion of one run and the start of the next run (with this trolley) leads to a flexibility and productivity improvement as enabler for a better repair production coating set up.@paragraph@A second key point of the paper is the contribution of an advanced, computerized process monitoring and control, to the aforementioned flexibility as well as to an improved quality statistic.
A4-2-5 EB-Preheating Technology and Equipment for Thermal Barrier Coating
C. Deus (Von Ardenne Anlagentechnik GmbH, Germany); U. Liess ( Von Ardenne Anlagentechnik GmbH, Germany); C. Melde (Von Ardenne Anlagentechnik GmbH, Germany)
While EB preheating of gas turbine components had been established in the TBC research community for years, the large-scale industrial application of this advanced preheating technology for production purposes - primarily for industrial gas turbine parts - emerged only 2 years ago. This conceptual innovation had to be supported by sophisticated solutions in EB gun design as well as beam deflection hard- and software.@paragraph@ A high precision high frequency beam deflection system was developed, providing outstandig performance in scanning a 200x800 mm@super 2@ wide evaporation field at frequencies above 10kHz. A fast and completely uniform heating can be achieved by supplying different regions of the heated parts with power densities exactly matched to their mass distribution. A dedicated soft/hardware-combination ensures that these optimized power density distributions follow the varying positions and outlines of parts that rotate during the heating cycle.@paragraph@ The prospect of expanding this technology to the more sensible aircraft engine market is discussed, addressing well-known concerns about reproducibility, stability and traceability of the technological parameters.
A4-2-7 Effect of Molten Particle Speed and Surface Temperature on the Properties of HVOF CrC/NiCr Coatings
W-C. Lih, Y.W. Lee, I.C. Hsu, W.J. Chang, Z.R. Wu (Industrial Technology Research Institute, Taiwan, ROC)
High velocity oxy-fuel (HVOF) is a promising process for the preparation of CrC/NiCr coatings to resist wear environment at elevated temperature up to 800C. During thermal spraying process, the speed and surface temperature of in-flight molten particle are two key factors affecting the sprayed coating properties. Coating deposited by higher kinetic energy and lower surface temperature molten particles is expected to be dense and hard. In this work, a two-color pyrometer in-flight particle sensor based on the Planck Law of thermal radiation was employed to monitor molten particles’ speed and surface temperature. Microhardness, porosity content, oxygen content and microstructure of coatings prepared by different molten particles speed and surface temperature will be discussed.
A4-2-8 Comparison of HVOF and LPPS Sprayed CoNiCrAlY Coatings
C.M. Eminoglu, D. Bucci, J. Helm (Sermatech International)
MCrAlY overlay coatings for corrosion and/or oxidation protection on IGT components with Low Pressure Plasma Spray (LPPS) are considered by industry as state of the art. The high initial investment and maintenance cost of LPPS units, however, put the industry in a position to search for alternatives to this method. A worthy alternative for LPPS is seen to be High Velocity Oxy-Fuel (HVOF) process with low initial investment and maintenance cost. HVOF MCrAlYs possess low porosity, low oxide content and high bond strength. @paragraph@ Comparison for corrosion resistance is made between HP/HVOF (High Pressure/High Velocity Oxygen Fuel) sprayed CoNiCrAlY and LPPS sprayed CoNiCrAlY. Additional comparison between HP/HVOF sprayed CoNiCrAlY and NiCoCrAlY is made under the same testing conditions. Corrosion/oxidation behavior of HP/HVOF and LPPS sprayed coatings is examined by high temperature oxidation and corrosion burner rig. Erosion results are also included.
A4-2-9 LPPS Thin Coatings for High Temperature Applications
P.J. Meyer, M. Loch (Sulzer Metco, Switzerland)
This paper discusses a new and novel method to apply metals and ceramics to various substrates at rapid rates over moderately large areas. The vacuum plasma process allows plasma cleaning of conducting substrates and coating on either hot or cold surfaces. The paper describes the process and equipment involved and presents some coating data for typical metal and ceramic materials. This method can produce coatings from a few microns to millimeters thick in a relatively short time. Typical deposition efficiencies for metallic and ceramic powder are approximately 80% at feed rates of 150 grams per minute. An even coating has been deposited over 0.5 m@super2@ at a rate up to 10 microns per minute.
A4-2-10 Ceramic/Metallic Coatings on Metals or Ceramics by Use of 2.450 Microwave Radiation
R. Roy, J.P. Cheng (The Pennsylvania State University); D. Agrawal ( The Pennsylvania State University)
Our unexpected recent success in sintering of virtually all (commercial) powder metal bodies (up to 15 cm in diameter) in a microwave field, has now led to the utilization of 2.450 GHz radiation for the successful coating of powdered metals or compositions such as WC-10%Co on bulk metal and powdered metal or certain ceramics. Both thin (1-10 µm) and thick (mms) coatings can be applied in this manner on a wide range of substrates. The results of detailed characterization in extensive experiments using different substrates and different coatings in multimode and single mode cavities will be printed. It is clear that microwaves must be added to the processes available for coatings.
A4-2-11 Use of 83 GHz Gyrotron Radiation for Coatings on Metals and Ceramics
K. Cherian (Center for Remote Sensing Inc.); A. Fliflet (US Naval Research Laboratory); S. Ganguly (Center for Remote Sensing Inc.); R. Roy (The Pennsylvania State University)
New processes for the application of coatings are very rare. The 83 GHz gyrotron offers such an opening. Studies of a variety of materials ranging from simple oxides and carbides to complex ceramic glazes as coatings on metals and ceramic have been studied and ceramics have been conducted. @paragraph@ We describe both the best experimental parameters and the most successful coatings obtained so far.
A4-2-12 Stability of Aluminum Nitride Films in Oxidizing Environments
D.K. Kalyanasundaram, M. Graham, A. Salifu, R. Ramsier, E.A. Evans (University of Akron)
Aluminum nitride oxidizes rapidly, changing its optical and electrical properties. Stability of aluminum nitride against oxidation is important for processing and, ultimately, device performance. Aluminum nitride films were deposited onto glass and fused quartz by RF sputtering to study the effects of deposition conditions on environmental stability. The quality of aluminum nitride films depends on the deposition conditions. The degradation of aluminum nitride was studied in an oxygen plasma, under an ozone-rich environment, and within an ashing furnace. The relationship between plasma power, deposition pressure, and plasma composition on film quality and the resulting degradation rate will be presented. We will also present results on the effect of different passivation layers. These relationships are important not only for limiting oxidation during and after deposition but also for identifying growth regimes for high quality aluminum nitride.