Nozzle coating extends service life

CF6-80C2 LPT nozzle
OEM internal coating process approved

CF6-80C2 stage 1 & 2 LPT nozzles are manufactured with an aluminide coating on the outside only. Their unprotected internal cavities are prone to sulphidation attack which may result in the early scrapping of these parts. A new OEM approved internal coating process is now available from Lufthansa Technik Turbine Shannon (LTTS), improving the durability and extending the life of these parts. 

Removing and achieving

To extend the service life of CF6-80C2 LPT nozzles, GE has issued a Service Bulletin (SB 72-1222) for the coating of the internal surfaces of the nozzle. Complementing its extensive repair capability on these parts, LTTS has developed the capability to apply this Service Bulletin. The internal coating repair involves two main process steps: The first is removing the sulphidation from the surfaces of the internal cavities, the second is achieving a uniform internal coating in accordance with the OEM requirements. 

Accurate multi-stage cleaning process

In order to facilitate effective cleaning and coating of the internal cavities it is necessary to remove the plenum cover (stage 1 parts) and the end caps (stage 2 parts). To comply with the Service Bulletin, LTTS has developed an advanced multi-stage cleaning process and at the end of this process the internal cavities are inspected using a Borescope to ensure complete removal of sulphidation / corrosion by-products. At the same time ultrasonic thickness inspection is used to verify that the parts have adequate wall thickness prior to processing the parts through the full repair process. 

Process of external and internal coating

LTTS utilizes a Vapour Phase coating process to aluminide coat the external surfaces of the nozzles and have introduced a CODEP powder coating process to apply the internal coating. This involves packing the cavities with a premixed powder in accordance with the OEM's material specification. The parts are then processed through a furnace cycle to a temperature of 1060°C in an Argon atmosphere and the powders are removed from the cavities post coating. 

Warranties for the customer

Coating samples are used to qualify the internal and external coating for each coating run and analysed to verify the thickness and integrity of the coatings. The entire process guarantees, that customer engines equipped with these nozzles actually show an improved durability and an extended service life with the associated cost savings.