Erosion in Large Gun Barrels Report of Committee on Gun Tube Erosion (1975) / Chapter Skim
Currently Skimming:
TRANSFER OF TECHNOLOGY FROM OTHER FIELDS TO THE EROSION OF GUN BARRELS
TRANSFER OF TECHNOLOGY FROM OTHER FIELDS TO THE EROSION OF GUN BARRELS
Pages 41-55
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 41... ...
Similar destructive phenomena limit the useful life of internal combustion engines, metal cutting tools and the dies used for forming metal in the casting, forging and extrusion processes. Discussion of wear problems in each of these fields follows, as does a summary of those corrective measures used in each area which might also be applicable to gun barrel use.
|
From page 42... ...
Steps taken by engine designers to minimize the problem include cooling of the valve, se^ction of valve materials with good physical properties and high corrosive resistance at elevated temperatures, and protective coatings for the sealing surface.
|
From page 43... ...
The valve seat, formed in a mass of relatively well-cooled metal, is less prone to catastrophic "guttering" or "burning" than the valve itself. In typical automotive use, for instance, the grey cast iron of the cylinder head has long been adequate as a seat material and the seat is simply machined into the iron.
|
From page 44... ...
has been helpful in engines of moderate specific output. For high-output or heavy-duty applications, it has been necessary to use valve seats of superior materials inserted into the cast iron cylinder heads.
|
From page 45... ...
The Chevrolet Vega automobile engine block is cast of high-silicon aluminum alloy and the piston rings run on the aluminum surface - which has been electro-etched to make the silicon particles protrude microscopically above the aluminum. Cast iron, however, is the norm.
|
From page 46... ...
is based upon an Elnasil-coated trochoid housing with apex seals of an iron compound akin to piston ring material (Goetzewerke's IKA)
|
From page 47... ...
They can be either cast or wrought. Traditionally, engine wear is determined by disassembling the engine after running and measuring the individual parts with conventional measuring tools micrometers, dial bore gages, etc.
|
From page 48... ...
The same basic technique has since been used in laboratory work on the nature of the wear process, using simply a Knoop diamond and a measuring microscope to measure very small amounts of wear in bench tests. An application of this technique to the wear of gun barrels is questionable as the scuffing, smearing and other plastic deformation involved will tend to fill the indentation with debris and obscure any measurement of real wear.
|
From page 49... ...
To withstand such extreme conditions, cutting tools must be refractory enough to retain their shape under high operating temperatures, hard enough to resist the erosive action of the chip and ductile enough to avoid chipping when microwelds which form on the tool face are broken. Material characteristics that are useful in prolonging tool life should be useful in preventing gun barrel erosion.
|
From page 50... ...
The strong tendency for clean metals to adhere when operating in sliding contact is frequently reduced by use of cutting fluids which contaminate the sliding surfaces and hence prevent adhesion and galling. Some of the extreme pressure additives used in cutting fluids might prove useful if a spray coating were to be used at the breech end of a gun between firings or if it would be possible to coat the outside surfaces of shells with suitable boundary or solid lubricants.
|
From page 51... ...
This is due to the formation of thermal fatigue cracks that result from the thermal stresses that arise as the tool is alternately heated and cooled. High speed steel tools that cut intermittently are helped by strong cooling since this class of tool materials is ductile enough to avoid cracks due to thermal shock and thermally induced fatigue.
|
From page 52... ...
.from as little as only a few pushes on certain extrusion dies, to more than a quarter of a million parts produced in permanent mold cast dies, for example. For dies and molds that run hot, more highly alloyed tool steels are the usual mold or die materials.
|
From page 53... ...
Another possibility that is not generally a feature of the materials and coating systems used for casting, forging and extrusion but that could be an important aid in improving life of gun barrels would be the use of gun tube materials or surface coatings that would provide improved resistance to the chemical corrosion and oxidation aspects of the gun tube erosion mechanism.
|
From page 54... ...
All of this, while not completely unrelated to gun tubes, does not suggest useful solutions.
|
From page 55... ...
However, it is recommended that basic theoretical understanding now being obtained by the gas turbine industry be monitored for possible application to the gun erosion problem. Technology transfer, if it eventuates, would be most likely from industrial gas turbines, which operate in industrial atmospheres and use fuels containing contaminents such as sulfur.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.