Closed Loop Electric Arc


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Use of state of the art electric arc spraying for repairing aircraft engines.

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Closed Loop Electric Arc

  1. 1. By Marcel van Wonderen Process Technology Department Central Engineering KLM Engineering & Maintenance Schiphol-Airport The Netherlands
  2. 2. <ul><li>Content </li></ul><ul><li>Introduction </li></ul><ul><li>Chronological </li></ul><ul><li>Pictures </li></ul><ul><li>Details </li></ul><ul><li>Features </li></ul><ul><li>Metallurgical results </li></ul><ul><li>Applications </li></ul><ul><li>Conclusions </li></ul><ul><li>Developments </li></ul>
  3. 4. KLM’s chronological order of acquiring thermal spray equipment: - ‘69/’70: Flame spray equipment (including fusion), in a brick room with water curtain - 1972: Plasma spray equipment (handheld gun, turntable, powder feeder, manual control console) - 1987: First robotized plasma cabin with PLC control (first Airline in Europe) - 1992: Programmable special purpose plasma spray machine for ‘Fan disks’ - 1997: New cabin for electric arc spraying at the B&V department - 1995: New dust collecting & filtration system for the ‘brick room’ - 1998: Upgrade of plasma spray equipment towards CE marking - 1993: Introduction of electric arc spraying - 2004: New ‘State of the Art’ robotized spray cabin with unique features (like high efficiency plasma) - 1999: New multi functional turntables - 2001: New PLC programmable horizontal and vertical traverses - 2005: First to get new closed loop electric arc spray system of Praxair-TAFA type 9935
  4. 5. Improvements needed : High amount of fume and dust emission. Lower than desired deposit efficiency Process Instability ; a) Voltage output fluctuations b) Possible feed rate changes, arcing, micro-welding of wires to the current transfer tips c) Changes of atomizing airflow rate Coating non-homogeneity, inclusions of unmelts and sometimes high porosity ; a) Electrical voltage parameters ripple and pulsation; b) Instability of wire feeding; arcing; c) Instability of airflow rate mentioned above Improper control or lack of control; a). Feedback voltage and air pressure or flow rate signals are taken from the console b). Air hose restrictions, resistance and bending are not taken into account. c). Electrical resistance of power leads and their connections to a power source and to a gun are not taken into account. High incoming air supply pressure ; Big pressure drop inside control systems requires high incoming pressure. Often only 80-90 psi (5.5–6.2 bar) of air pressure is available. Therefore more difficult of producing as dense a coating as possible
  5. 6. Picture at the ITSC’05 in Basel, Switzerland: KLM purchases first type 9935 closed loop electric arc spray system of Praxair-TAFA
  6. 7. Detail pictures of the 9935 CoArc:
  7. 8. Features of the new 9935 Praxair-TAFA Closed-loop electric arc spray system: <ul><li>Touch screen operators console </li></ul><ul><li>Lower atomizing voltage spraying </li></ul><ul><li>Ultra high air flow capability </li></ul><ul><li>Voltage and air pressure measuring at the gun head </li></ul><ul><li>Wire usage counter and “out” monitor </li></ul><ul><li>Recipe storage </li></ul><ul><li>Data acquisition </li></ul><ul><li>Higher deposit efficiencies </li></ul><ul><li>Low, HVOF-like coating porosity and low oxide levels </li></ul><ul><li>“ Pull” and “push-pull” configurations </li></ul>
  8. 9. Metallurgical and tensile bond strength results of the new 9935 Praxair-TAFA closed loop electric arc spray system : Example of Cupper-Zinc-Silver alloy CuZnAg: tensile bond strength average 64 N/mm 2 (min. req. is 20,7 N/mm 2 ref. GE SPM 70-49-44) Non-Heat Treated Heat Treated 2 Hours at 399°C Heat Treated 2 hours at 468°C
  9. 10. Examples of Inconel 718, Nickel-Aluminum and Cupper-Nickel-Indium: Evaluation according GE SPM 70-49-xx Evaluation according GE SPM 70-49-yy Evaluation according GE SPM 70-49-zz
  10. 11. Voltage during spraying with traditional system Voltage during spraying with new ‘state of the art’ closed loop electric arc spray system
  11. 12. Typical applications: <ul><li>Parts: Coatings: Function: </li></ul><ul><li>- HPC stator case Al Abradable </li></ul><ul><li>- CRF Inc 718 Dimensional rest. </li></ul><ul><li>- Fan frame assy NiCrAl Dimensional rest. </li></ul><ul><li>- Cooling & Vent Seal CuZnAg Abradable </li></ul><ul><li>- Fanblades CuNiIn Anti-fretting </li></ul><ul><li>- #1 Bearing Housing Mo Anti wear </li></ul><ul><li>- Housing Sump 4 brg NiAl Dimensional rest. </li></ul>
  12. 13. Conclusion - KLM is investing in new ‘State-of-the-Art’ thermal spray equipment in order to establish a “center of excellence” in thermal spraying within the Aircraft MRO market. - KLM wants to stay in the front line of new developments
  13. 14. Future : <ul><li>Testing Zinc and Aluminum spraying on composite Aircraft materials as anti-static coating </li></ul><ul><li>Testing new (cored) wires for Aircraft Industry </li></ul><ul><li>New ‘light’ gun (only push system). EM-14 </li></ul><ul><li>Development of internal spray gun. </li></ul>