Erosion and corrosion on gas turbine engine compressors is a major problem that costs the DoD billions annually in maintenance and spare parts. During the first Gulf War, the challenges of operating rotary wing aircraft in high-sand and maritime environments clearly brought this issue to the forefront. Engines were removed for low power in some cases after only 50 hours of operation – greatly burdening the warfighters in providing mission-capable air vehicles.
Through a CTMA supported project, NAVAIR is currently evaluating MDS Coating’s Black Gold® erosion/corrosion protection coating on the GE Aviation T700 engine installed on NAVAIR’s MH-60R/S Seahawks and the Marine Corps’ AH-1Z Viper and the UH-1Y Venom helicopters.
“Helicopter engines were not initially designed to be very tolerant of sandy environments. Depending on the type and chemistry of the sand and the temperature of the engine, it affects the operability and efficiency,” says Robert Sartorelli, senior engineer, GE Aviation.
During the multi-year project, NAVAIR completed an engine sand ingestion test (SIT) and is involved in ongoing airworthiness certification tests. The SIT allowed for a direct comparison of uncoated and coated compressor airfoils. The results demonstrated the BlackGold® coating’s ability to maintain the profile and thickness of the compressor airfoils – allowing the compressor to better retain engine performance throughout operations. This results in increased engine time-on-wing, greater fuel efficiency, reduced maintenance activities and lower operational costs.
“The initial funding for this CTMA project was provided in 2010,” says Marcio Duffles, Vice President, Business Development, MDS Coating. “In addition to protecting against erosion and corrosion, our coatings can be supplied with very low, ‘mirror-like’ surface finish values that retain their surface finish during operations. Beyond the performance retention benefits, maintaining a smooth compressor airfoil surface could possibly help mitigate fouling build-up and reduce the maintenance frequency of compressor washes.”
The coating helps the original equipment manufacturers support customer requirements and supply engines that last longer. The Navy took a stage-by-stage approach in evaluating the behavior of the coating to ensure it met efficiency and cost requirements.
“We took time to test and determine where within the engine an erosion/corrosion coating makes the most sense to apply with respect to effectiveness for maximum value,” says Chris Rowe, Turboshaft/Turboprop Design Tech Lead, NAVAIR. “We are preparing to conduct a field evaluation and are also working on documentation to get it into service, fleet-wide.”
Erosion has been a struggle for both the Department of Defense as well as the commercial transportation industry. The Department of Energy conducted projects to evaluate the benefits of using a nanocoating on compressor blades of gas turbine engines through their Industrial Technologies Program. These benefits have included:
- Reduced carbon emissions due to higher compressor efficiencies; a 1% increase in compressor efficiency decreases carbon dioxide emissions by 1-4 pounds-mass per hour.
- Increased engine power due to greater use of inlet fogging, which can augment power output for an electricity-producing power plant by 7-8% under certain conditions.
- Increased productivity due to extended engine lifetimes.
But with our nation’s security at risk, maintaining our aircraft fleet is a top priority. “With this coating, we expect to increase our reuse of the blisks by 2X,” says Rowe. “Readiness is a peak interest and ensuring we have the coatings in just the right places will help as well as optimize repair cost. I am thrilled that this product is finally being fielded for the fleet.”
Duffles feels that working with NCMS through the CTMA Program was extremely helpful in facilitating this project. Because of NCMS support, the MDS Coating team could focus on engineering and customer service.
“The performance of the coating so far, in action, has been very impressive,” says Sartorelli. “I’m looking forward to seeing how it performs in a field test.”