The Role of Carburization in Gun Barrel Erosion and Cracking PDF Download
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Author: C. C. Morphy
Publisher:
ISBN:
Category :
Languages : en
Pages : 91
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Book Description
The subject program is part of a continuing effort to identify distinct mechanisms that contribute to gun barrel wear and erosion. The chemical effect of a carburizing atmosphere in a gun tube was the main topic for investigation in this program. Experiments were conducted in the Shock Tube Gun (STG), a ballistic compressor, designed and developed by Calspan Corporation. This facility can compress mixtures of pure gases to simulate propellant gas flow condtions and cycle time experienced in large caliber guns. Test were conducted with a mixture of argon and nitrogen to delineate the threshold of simple melting erosion which served as a chemical inert baseline. Progressive substitution of carbon monoxide for nitrogen in the mix quantified the carburizing effect as a function of CO concentration. Subsequent tests were conducted with a gas mixture containing carbon monoxide, argon and helium to measure the carburizing effect as a function of cycle time. The basic carburizing effect was observed to be a shift in the erosion threshold to less severe convective heating conditions in response to surface chemistry. The magnitude of the shift appeared to be directly proportional to heating cycle time.
Author: C. C. Morphy
Publisher:
ISBN:
Category :
Languages : en
Pages : 91
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Book Description
The subject program is part of a continuing effort to identify distinct mechanisms that contribute to gun barrel wear and erosion. The chemical effect of a carburizing atmosphere in a gun tube was the main topic for investigation in this program. Experiments were conducted in the Shock Tube Gun (STG), a ballistic compressor, designed and developed by Calspan Corporation. This facility can compress mixtures of pure gases to simulate propellant gas flow condtions and cycle time experienced in large caliber guns. Test were conducted with a mixture of argon and nitrogen to delineate the threshold of simple melting erosion which served as a chemical inert baseline. Progressive substitution of carbon monoxide for nitrogen in the mix quantified the carburizing effect as a function of CO concentration. Subsequent tests were conducted with a gas mixture containing carbon monoxide, argon and helium to measure the carburizing effect as a function of cycle time. The basic carburizing effect was observed to be a shift in the erosion threshold to less severe convective heating conditions in response to surface chemistry. The magnitude of the shift appeared to be directly proportional to heating cycle time.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 92
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Book Description
Experiments to determine the individual contributors to gun barrel erosion in an oxidizing atmosphere were conducted in the Shock Tube Gun (STG), a ballistic compressor, designed and developed by Calspan Corporation. This facility can compress mixtures of pure gases and can generate flow conditions and cycle times similar to those experienced in large caliber guns. Tests were conducted with a mixture of argon and nitrogen to define the threshold erosion for an inert baseline. Small concentration of oxygen were substituted for nitrogen in the mix to quantify the oxidation effect. Subsequently, tests were conducted with various gas mixtures containing carbon dioxide, which dissociates to produce oxygen when compressed to high temperatures. The basic oxidation effect was observed to be nearly linear increase in erosion with oxygen concentration. A corresponding shift in the erosion threshold to less severe convective heating conditions was observed in response to surface chemistry. A similar effect was observed for carbon dioxide mixture where erosion was correlated in terms of the equilibrium concentration of oxygen at peak pressure. Surface cracking was observed and found to be most severe near the erosion threshold where the oxide layer was thickest. A white layer was observed in tests with oxygen in the absence of carbon dioxide.
Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 224
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Category : Ordnance
Languages : en
Pages : 464
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Category : Ceramics
Languages : en
Pages : 528
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Author:
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ISBN:
Category :
Languages : en
Pages : 15
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Book Description
An update is provided for the previously-presented gun barrel thermochemical erosion modeling code. This code addresses wall degradations due to transformations, chemical reactions, and cracking. As a predictive tool, it provides analysis and design information that is either unattainable or expensive by experiment. Single- or multiple-shot comparisons can be made of either the same gun wall material for different rounds, or different gun wall materials for the same round., this complex computer analysis is based on rigorous scientific thermochemical erosion considerations that have been validated in the reentry nosetip and rocket nozzle/chamber community over the last forty years. A gun system example is used to illustrate the five module analyses for chromium and gun steel wall materials for the same round. The first two modules include the somewhat modified standard gun community XNOVAKTC interior ballistics and BLAKE nonideal gas thermochemical equilibrium codes. The last three modules, significantly modified for gun barrels, include the standard rocket community two-dimensional kinetics!mass addition boundary layer (TDK/MABL), gas-wall thermochemistry TDK/CBT), and wall material ablation conduction erosion (MACE) codes. These five analyses provide thermochemical ablation, conduction, and erosion profiles for each material as a function of time, travel, and rounds. For the gun system example, at two axial positions, with cold and hot firing rates. predictions of rounds required to achieve 0.040-inch wall loss are made for cracked and uncracked 0.005-inch chromium plated A723 steel and A723 steel alone. Thermochemical erosion increases by a factor of about 2.0 from cracked chromium plated A723 steel to A723 steel alone. For a given%wall, thermochemical erosion decreases by a factor of 1.4 from the hot to the cold firing rates.
Author: William T. Ebihara
Publisher:
ISBN:
Category :
Languages : en
Pages : 26
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Book Description
Metallurgical analysis was conducted on 7.62mm machine gun barrels, in the chromium-plated and unplated conditions, to describe the erosion process. The chronological analysis involved the examination of severly eroded gun barrels as well as those subjected to test firings of 1 to 3000 rounds. Inherent defects in the form of cracks were noted in the chromium plate prior to firing. These cracks were extended to the chromium-steel interface as early as the first round; thus the underlying steel was exposed to the reactive environment. Continued firing resulted in the propagation of these cracks into the steel substrate followed by crack-branching. Branching proceeded until linkup was achieved, which resulted in the removal of chromium plate steel fragments. The factors considered to be responsible for crack extension include gaseous and liquid metal reactions. The type of erosion found in unplated steel gun barrels was in contrast with that of the plated barrels in that substrate-cracking was delayed and land wear occurred much earlier in the firing sequence.
Author:
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ISBN:
Category :
Languages : en
Pages : 31
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Book Description
Specimens containing white layers were taken from the bore surface of the unplated and chrome plated fired gun tubes. These were examined metallographically and the presence of various white layers was established. The chemical and structural nature of these layers was determined by Auger/ESCA and x-ray diffraction techniques. The outermost white layer contained up to seven percent carbon and was identified as cementite - Fe3C. The subsequent white layers has approximately one percent carbon and were identified as high carbon austenite. The significance of these results is discussed in terms of solution and diffusion of carbon from burnt propellant are responsible for the formation of white layers and are the cause of erosion and cracking in the bore surface. During heating and cooling of fired gun barrels, stresses are generated by the differences in the coefficient of expansion and volume changes associated with cementite, austenite, and matrix metal phases. Cracks are produced in the white layer and are propagated in the substrate steel matrix. The high carbon- containing phases are lower melting than steel. These molten phases are eroded away by the sweeping hot propellant gases, thereby eroding the bore surface of the gun barrel. These and other results are discussed in terms of their effects on erosion and wear in the gun barrel bore surfaces.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 456
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 99
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Book Description
The subject program is part of a continuing effort to identify distinct mechanisms that contribute to gun barrel wear and erosion. The thermochemical effects of altering the CO/CO2 ratio of a propellant gas in a gun tube was the main topic for investigation in this program. Experiments were conducted in the Shock Tube Gun (STG), a ballistic compressor, designed and developed by Calspan Corporation. This facility can compress mixtures of pure gases to simulate propellant gas flow conditions and cycle times experienced in large caliber guns. Tests were conducted with mixture ratios of carbon monoxide and carbon dioxide that characterize the normal range of CO/CO2 ratios found in propellant gas, i.e., 2.0 to 8.1. Progressive substitution of carbon monoxide for nitrogen in the mix quantified erosion as a function of increasing Co concentration or CO/CO2 ratio. Subsequent tests were conducted with gas mixtures containing double the amount of carbon monoxide and carbon dioxide but with the same effect CO/CO2 ratio, to measure erosion as a function of absolute reactant concentration for the two gas species. The basic chemical effect was observed to be a shift in the erosion threshold to less severe convective heating conditions in response to increasing the CO/CO2 ratio above a value of 5.6. The magnitude of the shift appeared to be directly proportional to the absolute concentrations of the two reactant gases. Variation of both CO/CO2 ratio and absolute amounts of the two gases resulted in distinct changes in specimen surface characteristics, both at near threshold and above threshold flow conditions.
