U.S. patent application number 09/363651 was filed with the patent office on 2001-10-18 for weapon barrel having a hard chromium inner layer.
Invention is credited to RECKEWEG, HORST, SCHLENKERT, GERT, WAGNER, HARTMUT.
Application Number | 20010029689 09/363651 |
Document ID | / |
Family ID | 7875873 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010029689 |
Kind Code |
A1 |
SCHLENKERT, GERT ; et
al. |
October 18, 2001 |
WEAPON BARREL HAVING A HARD CHROMIUM INNER LAYER
Abstract
A weapon barrel includes a hard chromium layer provided on an
inner barrel surface. The hard chromium layer contains at least 500
fissures/cm in a cross-sectional plane.
Inventors: |
SCHLENKERT, GERT;
(DUSSELDORF, DE) ; WAGNER, HARTMUT; (UNTERLUSS,
DE) ; RECKEWEG, HORST; (HEILIGENHAUS, DE) |
Correspondence
Address: |
VENABLE BAETJER HOWARD AND CIVILETTI LLP
P O BOX 34385
WASHINGTON
DC
200439998
|
Family ID: |
7875873 |
Appl. No.: |
09/363651 |
Filed: |
July 30, 1999 |
Current U.S.
Class: |
42/76.02 |
Current CPC
Class: |
C25D 3/04 20130101; Y10T
428/12632 20150115; F41A 21/04 20130101 |
Class at
Publication: |
42/76.02 |
International
Class: |
F41A 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 1998 |
DE |
19834394.9 |
Claims
What is claimed is:
1. A weapon barrel having an inner surface and comprising a hard
chromium layer provided on said inner surface; said hard chromium
layer having at least 500 fissures/cm in a cross-sectional
plane.
2. The weapon barrel as defined in claim 1, wherein said hard
chromium layer has an upper surface containing at least 150
fissures/cm.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority of German Application
No. 198 34 394.9 filed Jul. 30, 1998, which is incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a weapon barrel provided with an
internal, wear-reducing hard chromium layer including a plurality
of microfissures.
[0003] The hot powder burst generated upon firing of ammunition
leads to abrasive and erosive wear phenomena in the unprotected
inner wall of a weapon barrel usually made of steel. Such phenomena
adversely affect the range and accuracy of the weapon and lead to a
premature fatigue of the weapon.
[0004] It is known to provide the inner wall face of a large
caliber weapon barrel with a hard chromium layer for reducing an
erosive barrel wear, as disclosed, for example, in German
Offenlegungsschrift (application published without examination) 41
07 273. It has been found, however, that the high stresses caused
by the thermal shock upon firing may effect a gradual peeling of
the chromium layer. As a result, at those locations the weapon
barrel is no longer protected from the hot powder gases which thus
cause erosions there.
[0005] Since the peeling of the chromium layer is caused by the
microfissures which appear during the application of the chromium
layer, German Offenlegungsschrift 41 07 273 proposes to prevent
such a peeling by filling the microfissures with a low-friction
substance such as polytetrafluorethylene.
[0006] It is a disadvantage of the above-noted known weapon barrels
that their manufacture is relatively expensive. Further, the
microfissures embedded in the chromium layer cannot be filled with
the low-friction substance so that such fissures retain their
harmful effect inducing the peeling of the chromium layer.
SUMMARY OF THE INVENTION
[0007] It is an object of the invention to provide an improved
weapon barrel of the above-outlined type whose hard chromium layer
has, as compared to conventional hard chromium layers, an improved
resistance to thermal shocks without the need to fill the
microfissures with a low-friction substance.
[0008] This object and others to become apparent as the
specification progresses, are accomplished by the invention,
according to which, briefly stated, the weapon barrel includes a
hard chromium layer provided on an inner barrel surface. The hard
chromium layer contains at least 500 fissures/cm in a
cross-sectional plane.
[0009] According to the basic principle of the invention, the
number of microfissures in the hard chromium layer is intentionally
increased, as compared to weapon barrels having conventional hard
chromium layers, to such an extent that the hard chromium layer has
at least 500 fissures per cm or at least 150 fissures per cm on its
outer surface.
[0010] The result that an increase of the number of fissures within
the hard chromium layer leads to an improvement of the thermal
shock resistance of a weapon barrel is surprising, since the
microfissures of known weapons are precisely the triggering cause
for the peeling of the chromium layer and therefore the desideratum
has been to maintain the number of the microfissures as small as
possible. While the earlier-noted German Offenlegungsschrift 41 07
273 has also proposed to increase the number of microfissures after
the chromium layer is applied, the additional microfissures in the
upper face of the chromium layer serve merely for ensuring a better
adherence of the low-friction layer which fills the
microfissures.
[0011] The improved resistance to thermal shocks achieved by
increasing the number of fissures may be explained as follows: upon
firing a shot, the substantially brittle chromium layer is exposed
to high stresses which lead to substantial, thermally induced
expansions and tensions. As soon as the expansions exceed the
elastic limit of the chromium layer, they are taken up by the
already present and by the additionally appearing fissures. In
conventional chromium layers in which the number of fissures
measured cross-sectionally is approximately between 200/cm and
400/cm or the number of fissures measured on the surface of the
chromium layer amounts to approximately between 40/cm and 70/cm,
the fissures have to take up a relatively high proportion of the
expansion caused by the thermal shock so that they combine to form
relatively large fissures which are then responsible for the
peeling of the chromium layer.
[0012] The invention thus proposes to minimize the proportion of
the expansion as related to each individual fissure by
intentionally increasing the number of fissures so that a
combination into large fissures which are responsible for the
peeling of the chromium layer may no longer occur.
[0013] As concerns the different numbers of fissures on the upper
surface and across the hard chromium layer, it is noted that
essentially there is no preferred direction of the chromium fissure
frequency. The fissures are obtained during the galvanic deposition
of the chromium by the inherent high pulling stresses generated
during deposition. Upon reaching a certain minimum layer thickness
(approximately 5 .mu.m), fissures propagate in the chromium layer
from the surface and release a large proportion of the inherent
stresses. As the chromium deposition continues, the fissures are
grown over by a chromium layer which, after reaching a certain
thickness, likewise develops fissures. Such a process continues, so
that, as a result, a labyrinth-like structure is obtained. It is
understandable that the number of fissures per path length is
greater along the cross section of the chromium layer than along
the surface, since the fissures in the chromium layer are initiated
from its outer surface.
[0014] In addition to an improved thermal shock resistance, the
weapon barrel according to the invention has the further advantage
that a thicker chromium layer may be provided as compared to known
weapon barrels; such a thicker chromium layer provides for a better
protection of the barrel material. Further, the chromium layer
according to the invention is less sensitive to mechanical stresses
(for example, when contacting the projectile) and therefore such a
chromium layer may also find advantageous use in automatic
weapons.
[0015] The fissure frequency may also be controlled by the
composition of the electrolyte used for the chromium deposition, by
the temperature of the galvanizing process and by the manner in
which the current is guided; the optimal parameters may be
empirically determined for each mode of application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an axial sectional view of a weapon barrel
incorporating the invention.
[0017] FIG. 2 is a fragmentary sectional enlarged view taken along
line II-II of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] In FIG. 1 a weapon barrel 1 is shown which includes a
chamber 2. The inner face of the weapon barrel 1 is provided with a
hard chromium layer 3 having a thickness 4 and extending along the
barrel axis 5.
[0019] Turning to FIG. 2, the hard chromium layer 3 has a plurality
of microfissures 6 which, according to the invention, number at
least 500/cm in the cross-sectional plane or at least 150/cm on the
outer surface of the chromium layer.
[0020] It will be understood that the above description of the
present invention is susceptible to various modifications, changes
and adaptations, and the same are intended to be comprehended
within the meaning and range of equivalents of the appended
claims.
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