Thermo-chemical erosion in gun barrels

Robust Microencapsulated Silicone Oil with a Hybrid Shell for Reducing Propellant Erosion

: Heat transfer, melting, and erosion tests were conducted using a unique Shock Tube Gun Facility available at Calspan. Materials of interest were subjected to intense heating using non-reactive gas mixtures. Pure melting of materials was obtained at heating conditions representing those of actual guns. A computer code was formulated, written, tested, and shown to adequately normalize the gross thermal data, thus permitting determination of expected bore temperatures and/or material loss for given heating conditions. It was found that, although the bore surface temperature of steels tested in the non-reactive gases of the Shock Tube Gun achieved temperatures of the same magnitude as those in large caliber guns where bore surface cracking is produced, no similar surface cracking of steels was observed. It is concluded that chemical activity of gun gases is partially responsible for crack initiation in gun tubes. (Author)

Shock Tube Gun Melting Erosion Study.

Preparation and Characterization of Metatitanic Acid/Urea‐Formaldehyde Microcapsules as Wear‐Reducing Additives

A concise review on degradation of gun barrels and its health monitoring techniques

The reduction of barrel erosion by wear-reducing additives

: Gun barrel wear tests have uncovered the need for a small scale device to test barrel treatments like 'thick' chromium. Small caliber barrels have traditionally served this role, but results with high-firing rates used to produce measurable wear are ambiguous. An ideal erosion test device would be a small caliber gun with standard projectiles, cartridge cases and propellants which would produce wear comparable to wear in large-caliber guns. Interior ballistic tests were done with M2 or M9 propellant in place of the standard ball powder in the M55A2TP-T round to determine charge masses which would not exceed the peak chamber pressure of the reference M55A2TP-T round. The wear produced with the high-flame temperature propellants was estimated with the Frankle-Kruse empirical formula. The results showed an M9 propellant could be loaded to the same charge mass as the reference WC870 ball powder with a lower peak chamber pressure but 100 m/s higher velocity. The wear estimated for such a round is 5 micrometer/shot, comparable to wear -limited Army guns, but less than the desired 25 micrometer/shot (1 mil/shot) for an erosion test device. Hence the 20-mm gun with M9 propellant could be useful for evaluating chromium-plating for existing guns, but it has too little wear for conveniently assessing future platings and coatings.

Timothy L Brosseau

Papers

The reduction of barrel erosion by wear-reducing additives

Interior Ballistic Evaluation of High-Flame Temperature Propellants in 20mm Ammunition and Assessment as an Erosion Test Device