Thermally Stable Machine Gun Barrel

The proposed project seeks to take advantage of the success of an on-going Air Force Phase II SBIR and leverage the lesson’s learned with medium calibre barrel to apply the new technology to small caliber machine gun barrels. In the previous Phase I and on-going Phase II projects, the feasibility of producing a fully dense, non-micro-cracked Nanostructured cobalt–refractory metal alloy with co-deposited hard ceramic particles was demonstrated. The Nanostructured coating was found to have wear resistance equal to that of hard chrome coatings, but did not suffer from the same micro-cracked structure that chrome possesses, even after thermal cycling to 1832°F. Laser pulse testing simulating the heat input experienced in a 25mm medium caliber gun barrel (M242 with M919 propellant) showed no significant damage or microcracking as seen in hard chrome coatings. The absence of a micro-cracked structure in the Nanostructured coating is expected to result in increased performance over the current hard chrome coatings in the gun-barrel bore due to the lack of a pathway for the hot-erosion combustion gases to attack the base-metal, thus leading to a longer lifetime. Additional benefits of the Nanostructured coating relative to hard chrome include: faster deposition rates, lower power consumption during processing, and elimination of the health risks associated with hexavalent chromium (Cr6+). The specific objectives of the proposed program are to: (1) develop the tooling needed to apply the Nanostructured composite coating to the inner bores of small caliber (5.56mm/M249 or 7.62mm/M240) machine gun barrels (the current on-going Phase II SBIR is specifically investigating 20mm barrels), (2) perform actual field testing to demonstrate and validate the technology, and (3) define all critical technical parameters in a thorough process specification to allow the technology to proceed to facility demonstration/validation activities. Based on the results of these tests a full Implementation Assessment will be performed to determine whether performance and cost will make this a cost-effective solution for the various small caliber platforms used by the Navy.