Gas turbine engine degradation due to operations in austere environments has adversely affected both commercial and military aviation operations. When gas turbine engine compressor airfoils degrade due to particulate (sand, dust, volcanic ash, salt, and water) ingestion, engine performance deteriorates resulting in higher fuel consumption, increased emissions of pollutants, reduced engine reliability, increased engine maintenance and higher operational costs. Several Department of Defense weapon systems were experiencing an unacceptable level of erosion and corrosion from operating in austere environments such as Iraq, Afghanistan, and overseas. Particularly hard hit were engine compressors and compressor blades.
The Army, Navy, and Air Force identified the three engines that underwent demonstrations and field evaluations as part of the Commercial Technologies for Maintenance Activities initiatives. The AGT1500, T56, and T700 are installed in different platforms (two air and one tactical ground vehicle), yet all were experiencing unacceptable degrees of corrosion and erosion. All three projects were in response to engine compressor and compressor blade degradation from operating in excessive amounts of sand, dust, salt, water, volcanic ash, and other natural elements.
The first of the three engines tested with the MDS Coating BlackGold® was the AGT1500. Results of this test helped inform the testing protocol for the other two tests.
In this effort to determine the effects of compressor erosion and the benefits that a protective coating can offer, a sand ingestion test (SIT) was conducted at Anniston Army Depot in Anniston, Alabama on two (2) AGT1500 engines between May and September 2012. One engine had a protective coating applied on most of the compressor airfoils by MCT while the compressor airfoils on the other engine were uncoated. A cross section of the AGT1500 engine revealing the compressor airfoils is shown in Figure 1).
Figure 1: AGT1500 Compressor Cross-Section
The purpose of the test was to compare the erosion performance of compressor airfoils coated with MCT’s BlackGold®erosion and corrosion resistant coating (henceforth referred to as BlackGold®) to uncoated airfoils. This project documents the condition of the uncoated and coated compressor airfoils during and after the SIT.
The subsequent erosion and corrosion negatively affected the engine performance, life span, and reliability. All three projects were championed by the Office of the Deputy Assistant Secretary of Defense - Material Readiness and managed by the National Center for Manufacturing Sciences. MDS Coating’s BlackGold® was the coating tested in these three demonstrations.
The compressor and compressor blade degradation increase engine maintenance, fuel consumption and compressor airfoil replacement, which ultimately increases total operational costs. Protective compressor airfoil coatings provide protection for military engines in both harsh military environments and less austere operational environments. Protecting the compressor against erosion and corrosion results in retaining engine performance for longer operational hours. The performance retention leads to:
- Increased ETOW
- Lower compressor/engine repair and overhauls
- Decreased field repairs
- Lower maintenance costs
- Reduced scrap rates and consumption of critical materials such as titanium
- Lower fuel consumption
- Lower lifecycle costs
- Increased aircraft readiness and availability
Additionally, the erosion/corrosion resistant coatings have transitioned to both commercial aviation and industrial gas turbine engines with some applications and benefits listed below:
- Worldwide air carriers have been flying with MDS Coating’s BlackGold® coating since 2012 and have realized fuel and parts savings benefits.
- Delta Air Lines demonstrated fuel savings on a CFM56 coated engine Total projected average fuel savings per year over a typical engine tour of between 10 to 15 years will exceed 1%.
- Reduced fuel consumption directly leads to reduced CO2 and NOx emissions.
- Performance retention and spare parts savings in industrial gasturbine engines.