Gas turbine engine maintenance costs DoD approximately $8 billion annually. With DoD being challenged to reduce costs and improve readiness, engine maintenance is a significant focus area to explore and implement cost-saving initiatives. Low engine power is the primary cause for unscheduled engine removals, with compressor degradation being a leading contributor. Replacing compressor airfoils during maintenance repair operations, due to corrosion, is also a leading cost driver. Erosion resistant/corrosion resistant (ER/CR) compressor coatings have been developed and are designed to reduce wear on compressor airfoils in gas turbine engines, reducing overhaul and maintenance requirements and providing operational fuel savings. DOD has been involved in multiple programs to transition ER/CR coatings to gas turbine engines associated with helicopters, fixed-wing aircraft, and M-1 tanks. The purpose of this forum is to exchange information amongst the DOD and industry partners on the benefits, challenges, and results of using these protective coatings. We will discuss the best practices of transitioning ER/CR coatings, what other applications can benefit, and examine what next steps will efficiently promulgate this cost-cutting technology.
1300-1305: Welcome – Greg Kilchenstein (OSD-MR) Presentation
1305-1309: Administrative Notes – Debbie Lilu (NCMS)
1309-1335: AFRL Erosion Testing – Dr. Hartshorne (AFRL)
1335-1405: Turbofan and Compressor Coatings – Marcio Duffles (MDS Coating) Presentation
1405-1430: NAVAIR Engine Coating Experiences/Programs – Chris Rowe (NAVAIR)
1430-1455: AGT-1500 Army PM Abrams/Scavenge Fan Update – Kevin Kauth (DEVCOM)
1455-1500: Wrap-Up – Greg Kilchenstein (OSD-MR)
Event: On 25 May 2021, the Joint Technology Exchange Group (JTEG), in coordination with the National Center for Manufacturing Sciences (NCMS), hosted a virtual forum on “Engine Erosion & Corrosion Prevention”.
Purpose: The purpose of this forum was to examine and share information on engine erosion and corrosion prevention coatings available to the DoD maintenance community. The forum provided descriptions of erosion testing and coating developments and applications employed by the military Services as well as programs from industry.
Welcome: Greg Kilchenstein (OSD-MR) welcomed everyone to the forum and thanked the presenters and all the listeners for their attendance. He also stated how important engine erosion and corrosion prevention is in supporting continuous sustainment operations and readiness in the DoD maintenance community and how its’ development within DoD has expanded.
Administrative: This was an open forum. The presentations, along with questions and answers, were conducted through Adobe Connect. One of the presentations was available online at the JTEG website at http://jteg.ncms.org/ during the brief. A separate audio line was used. We had over 60 participants from across DOD, industry, and academia join in the forum.
AFRL Erosion Testing – Dr. Hartshorne (AFRL) described some testing capabilities that AFRL uses towards developing coatings to protect underlying components from environmental damage. The capabilities include a whirling arm rain erosion test facility, supersonic rain erosion upgrade, and a particle erosion apparatus to simulate ambient particle erosion. He listed the requirements of an organic coating for erosion resistance, and the combined effects of rain and sand erosion. He also discussed high temperature erosion to include standardized tests, the hot erosion rig upgrade, and calcium magnesium alumina silicate (CMAS) glassing.
Turbofan and Compressor Coatings – Marcio Duffles (MDS Coating) described the erosion / corrosion coating technology, to include their latest technology “Black Gold” and how it protects compressor airfoil surfaces. He followed up with a discussion of both military and commercial programs MDS is involved in to include CFM56 airfoils and the FAA Continuous Lower Energy, Emissions and Noise (CLEEN) programs. He concluded with a description of the benefits of protective coatings.
NAVAIR Engine Coating Experiences/Programs – Chris Rowe (NAVAIR) provided a presentation on Navy compressor and turbine coatings that explained the problem of dust ingestion and the solution areas. He described three fielded Navy/USMC platform coatings and also three ongoing evaluations. Additionally, he explained that turbine sand accumulation effects have been identified, and stated an advanced coating demonstration was completed in 2016 and NAVAIR is collaborating on a follow-on set of demonstrations of updated coatings.
AGT-1500 Army PM Abrams/Scavenge Fan Update – Kevin Kauth (DEVCOM) described the evaluations of the MDS erosion / corrosion resistant coating used on AGT 1500 compressor blades to include sand ingestion tests and comparisons of coated and uncoated blades. The coatings met all test and evaluation requirements. Kevin also discussed the use of MDS erosion / corrosion resistant coatings on the Abrams inlet scavenge fan and the wear on coated vs uncoated impeller blades. Findings support that the coating improves durability of the fan impeller, however the cost-to-benefit in this application was found to be not significant. Lastly, he described a compressor operational rig and advanced inspection opportunity rig that offers opportunities for operability testing and advanced on-rotor blade inspection.
Q&A – A Q&A occurred after each briefer finished their presentation. Questions and answers will be posted on the JTEG website with these minutes.
Closing Comments: Greg Kilchenstein thanked the presenters for their contributions and all the work being done to support engine erosion testing and coating developments and applications across the DoD, academia, and industry. He suggested continuing the information exchange beyond the forum and the importance of collaboration within the DoD maintenance community. Greg also informed everyone that this would be his last JTEG forum as he is retiring from government service this week. Several participants expressed their appreciation to Greg for all the contributions he has made towards the JTEG community.
- Obtain copies of the presentations once they are approved to post to a public website, and post to the JTEG website at http://jteg.ncms.org/ .
Next JTEG Meeting: The next scheduled JTEG virtual forum is 29 June 2021, 1:00 – 3:00 pm EST. The topic is “Ergonomics & Exoskeleton: Industrial Human Augmentation Systems”.
POC this action is Ray Langlais, firstname.lastname@example.org, (571) 633-8019
AFRL Erosion Testing – Dr. Hartshorne (AFRL)
Q1. How do you solicit compressor coatings for testing via your comprehensive tests?
A1. It depends on who is asking. Commercial and industrial customers can take advantage of the state-of-the-art coatings application, research, development, verification and qualification and testing, corrosion assessment and analysis, and erosion testing facilities through Cooperative Research and Development Agreements (CRADAs) with UDRI. You can visit their website.
Q2. Do you have a list of compressor coatings that meet your performance standards?
A2. Honestly, no. That’s part of why we are trying to stand up this effort….for over a decade now.
Q3. Do you envision a compressor coating spec that is specialized to the projected erosive media?
A3. We are in the first step with rain erosion coatings. It will vary by substrate. We are looking at polymer matrix composites.
Q4. Are all particulate erosion tests done on specimens or actual airfoils? If airfoils, what is the impingement location of the erosive particles?
A4. Actually, we do both. We have a standard airfoil specimen for both air and sand erosion rigs. The rigs are adjustable.
Q5. Do we have a reliable laboratory compressor blade erosion test that obviates the need to do full engine sand ingestion testing to validate coating benefits?
A5. I would say no at this point. I am not aware of it. We do coupon testing now. That is a much larger more complex system.
Q6. If we have a material in IRAD that might be suitable for use in these low-temperature erosion/corrosion situations, who should we contact to? (Regarding potential testing for sand/rain erosion behaviors)
A6. I would like to hear about it as well as the team lead for the coatings group, Diane. We can then put you in contact with the subject matter experts.
Q7. What are the composition of organic coatings used for erosion? Is walkway type of coating with particles suitable?
A7. I think mostly polyurethane coatings right now.
Comment. Great area to collaborate with commercial aircraft companies that have operated in those sandy regions for a long time.
Turbofan and Compressor Coatings – Marcio Duffles (MDS Coating)
Q1. Can you describe the technical qualification requirements as well as the BCA process needed to transition Black Gold to production compressor airfoils?
A1. The technical qualification requirements generally consist of high and low cycle fatigue tests, corrosion & erosion tests, and metallographic analysis. Since most tests are a function of material properties, in certain instances qualification by engineering similarity can be leveraged. The Business Case Analysis generally considers cost savings associated with reducing number of engine maintenance inductions, maintenance actions, parts savings and fuel savings. Other factors include reducing number of spare engines, increasing mission readiness and successfully completing missions.
Q2. Has Black Gold had the combined rain erosion followed by sand ingestion testing described by Dr. Hartshorne?
A2. We did rain erosion in 2007. After 2 hours the coating did not peel away. We have not done combined sand and rain.
Q3. What is the composition and process for the coating?
A3. The coating is applied via Catholic Arc Physical Vapor Deposition process. The coating is a multilayer ceramic-metallic matrix. Coating composition is proprietary.
Q4. How does Black Gold compare to other coatings (if there are any in the market)? What type of substrates can be coated?
A4. There are other coatings. MDS Coating is a world leader in the application of protective coatings with well over 6M coated airfoils supplied. The coating can be applied on titanium, nickel and stainless steel alloys.
Q5. What sort of blade repairs are being tested for compatibility with Black Gold? Does MDS install systems for performing Black Gold at a customer Depot/MRO Facility for coating repaired blades?
A5. We are doing that. That is part of the Continuous Lower Energy, Emissions and Noise III (CLEEN III) program. MRO’s are based on the business case. We would love to configure a system at a depot.
Q6. What work has been done with Black Gold on helicopter rotor blade abrasion strips?
A6. The BG coating has completed rain erosion testing on test specimens at AFRL’s rain erosion rig and successfully completed the 2 hour test without any coating delamination or peeling from the substrate. Erosion testing confirmed the coatings ability to protect against mass loss. Tests were also completed on rotor blade cover strips to confirm that the coating process does not deform the thin strips. The BG coating shows great promise in the application of rotor blade strips in protecting against both particulate and fluid erosion.
Q7. Does MDS use the ASTM G134 and G32 tests for Black Gold coating?
A7. MDS has developed its own internal erosion testing capabilities that better mimic the erosion outcomes typically found in gas turbine engine compressor systems. Some of these test specifications have been adopted by OEMs as part of the coating certification requirements.
NAVAIR Engine Coating Experiences/Programs – Chris Rowe (NAVAIR)
Q1. Are their timelines for the BCA’s for T56?
A1. I’m sure they have been blown past multiple times. I’m not sure of the current situation.
Q2. What information can you share regarding coatings on the F135 and/or Lift Fan for F-35?
A2. I can’t share that information. Marcio Duffles added that they are doing it commercially, but coatings don’t help with foreign object damage (FOD).
Q3. Any update on F404/F414 engines – F18?
A3. They are actively being looked at for turbine coating, not for fan coating or compressor coatings. We have struggled to get the attention of the compressor related folks.
AGT-1500 Army PM Abrams/Scavenge Fan Update – Kevin Kauth (DEVCOM)
Q1. Why are the T55 engine test data points relevant to the AGT1500 technical program?
A1. It was a concern at one point in time. The T55 is also a Honeywell product. We are trying to leverage some of the T-55 work to use on our project to vane time and money.