Accession Number : ADA330833

Title :   Hydrogen Cracking During Service of High Strength Steel Cannon Components

Descriptive Note : Final rept.

Corporate Author : ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET WEAPONS LAB

Personal Author(s) : Underwood, J. H. ; Troiano, E. ; Vigilante, G. N. ; Kapusta, A. A. ; Tauscher, S.

PDF Url : ADA330833

Report Date : SEP 1997

Pagination or Media Count : 27

Abstract : An investigation of environmental cracking during service of high strength steel cannon components is described. Two cases of cracking occurred in similar prototypes of an advanced cannon over a two-year period. The materials, components configurations, applied and residual stresses, environmental conditions, and the resulting cracking behaviors and SEM fracture surface characteristics are outlined. Laboratory hydrogen cracking tests of the cannon materials, finite element stress analysis, and stress intensity factor calculations were used to model the hydrogen cracking. The first cracking incident involved cracks up to 21-mm long near a pressure seal in an 1160 MPa yield strength ASTM A723 forged steel cannon tube, following five firing cycles. The second incident involved 50-mm long cracks that had grown after thirty firing cycles near the seal between two adjoining cannon components, one made from A723 and one from 1280 MPa yield strength PH 13-8 Mo stainless steel. The cause of cracking, given the presence of hydrogen-laden propellant products and susceptible high strength steels, was the sustained tensile stresses arising from assembly preloads required to maintain pressure seals between cannon components. Recommended preventative measures include reducing the strength level of the existing martensite steels, changing to austenitic nickel-iron base alloys, and redesign to lower the level of sustained tensile stress concentrations in areas subjected to propellant environments.

Descriptors :   *CRACKS, *STAINLESS STEEL, *HIGH STRENGTH ALLOYS, *GUN COMPONENTS, COMPUTATIONS, ENVIRONMENTS, STRESS ANALYSIS, FINITE ELEMENT ANALYSIS, TENSILE STRESS, ALLOYS, FRACTURE(MECHANICS), AUSTENITE, IRON, PROPELLANTS, SURFACE PROPERTIES, CONFIGURATIONS, RESIDUAL STRESS, PRESSURE VESSELS, NICKEL, HYDROGEN EMBRITTLEMENT, YIELD STRENGTH, ADVANCED WEAPONS, MARTENSITE, STRESS CONCENTRATION.

Subject Categories : Properties of Metals and Alloys
      Guns

Distribution Statement : APPROVED FOR PUBLIC RELEASE