ARL's new cold spray compound looks promising as helicopter sand erosion solution in harsh desert terrain
November 29, 2011
- Cold Spray may help fix the sand erosion problem that's causing helicopter maintenance.
- Findings were presented at the 2011 Annual Department of Defense Rotor Blade Erosion Working Group.
- Working group members include the Air Force, Naval Air Systems Command, Aviation and Missile Research, Development and Engineering Center, AMRDEC's Aviation Applied Technology Directorate, and ARL.
ARL may have found a combination of cold spray coatings to fix the sand erosion problem that's causing helicopter maintenance nightmares in Iraq and Afghanistan operations.
Fine particle sand in that region impacts rotorcraft blades during flight, eroding away at the blade composition - its coatings and its structure. This erosion to the baldes has cost the military almost a half a billion to repair or replace.
At a 2003 rotor blade summit, the Army reported a rotor blade demand rate for the Apache, Chinook, and Blackhawk during the previous 12 months, which included the invasion of Iraq, totaling more than $189 million, stating this demand was due in large to replacement because of blade degradation by sand erosion. New blades can cost up to $500,000 per helicopter. The value of rotor blades at risk in southwest Asia is an estimated $328 million.
A coating that looks particularly promising to withstand the harsh desert terrain was developed by ARL's Victor Champagne and Dr. Matthew Trexler of the Weapons and Materials Research Directorate's Materials (WMRD) and Manufacturing Science Division. The coating process involves coating the leading edge with high velocity air fuel applied tungsten carbide- cobalt (WC-Co) with cold sprayed niobium coating to the area away from the blade's leading edge.
These findings were presented at the 2011 Annual Department of Defense Rotor Blade Erosion Working Group meeting at Wright Patterson Air Force Base, Ohio, in September.
ARL's Marc Pepi, deputy chief of the Materials and Manufacturing Technology Branch, who helped amend the working group's charter, presented WMRD research related to rotor blade erosion resistance, cold spray efforts, while Richard Squillacioti of ARL's Specifications and Standards Office presented the development of standards for erosion of helicopter rotor blade materials.
In 2010, Pepi and Squillacioti were part of a joint winning team recognized for developing the military standard that provide a standardized test for particle/sand erosion resistance of materials used in leading edge erosion protection systems of helicopter rotor blades. Although this standard does not duplicate the real flight environment, it measures the amount of material eroded from a stationary specimen by particles accelerated in a high-speed gas jet. The standard is intended to cover testing of elastomers, other polymers (including reinforced plastics and composites), metals (including metal matrix composites), and ceramics.
Working group members include the Air Force, Naval Air Systems Command (NAVAIR), Aviation and Missile Research, Development and Engineering Center (AMRDEC), AMRDEC's Aviation Applied Technology Directorate, and ARL. The working group is currently considering a joint proposal for an Office of the Secretary of Defense effort on Corrosion Research and Development.
ARL's work in this area was initiated in 1991 by Victor Champagne who leads the Innovative Materials and Processing Team within WMRD. Champagne was an early ARL representative on the Erosion Working Blade Group. Champagne said he volunteered for Operation Desert Storm, and underwent training to accompany troops in the theater during the first Iraq war. He said the war ended soon after his training concluded but throughout the experience, he "became aware of the problems that soldiers faced in the war zone because he was working closely with military personnel who were in theater. The number one problem for the Army was sand erosion of helicopter rotor blades."
"As part of this effort, over 150 different coatings were tested and WC-Co emerged as a top candidate for this application," said Champagne. He said the coated blades will be sent to Ft. Eustis in Virginia "for evaluation in a 'whirling arm' test apparatus, which basically is a test rig designed to spin the blades as if they were on an aircraft."