The Role of Nitrogen in Gun Tube Wear and Erosion

Abstract : ARL has recently made discoveries in the area of interior ballistic propellant combustion product interactions with a gun tube bore. These discoveries were based on two hypotheses. The first was that the products could and are dynamically nitriding the bore of the gun, thus creating a nitride coating which inhibits the dissociation of CO and subsequently reducing the amount of carbon uptake. The second was that the combustion products richer in nitrogen have a lower temperature upon expansion in our experimental fixture as well as in a gun barrel. This is due to Joule and or Joule-Thomson cooling effects. Both of these hypotheses were proven and validated through numerical and experimental methods. Higher nitrogen containing combustion products have definitively been shown to have relatively lower erosivity with respect to those having lower nitrogen content. These results have revolutionized the gun propellant development community in that for the first time there is guidance for erosivity control through propellant chemical constituent formulation.