Coating apparatus – Gas or vapor deposition – Object embedded in particulate mass
Reexamination Certificate
1999-10-28
2001-07-10
Lund, Jeffrie R. (Department: 1763)
Coating apparatus
Gas or vapor deposition
Object embedded in particulate mass
C118S724000, C118S725000
Reexamination Certificate
active
06258172
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for boronizing a metal workpiece and an apparatus that has been developed for use in accordance with the teachings of the method.
BACKGROUND OF THE INVENTION
Boronizing is a process by means of which a wear and corrosion resistant coating is formed at a surface of a metal workpiece. The coating consists of a metal boride, such as an iron boride FeB or Fe
2
B.
A typical boronizing process involves placing a metal workpiece to be boronized in a container. The container is then filled with a powdered mixture of materials from which the boron needed for the thermochemical reaction is derived. The container is placed within a large furnace and the contents of the furnace are heated to a selected temperature. Upon heating, the powdered materials react with the surface of the metal workpiece to form a boride coating as a protective layer. When a sufficient time has elapsed for the coating to be completely formed as a strong integral layer about the workpiece, the container is cooled and emptied. The boronized workpieces are removed for inspection, testing, cleaning and further heat treatment, if needed. Spent powdered materials are discarded or recycled to the extent possible.
Setting up a boronizing facility is a capital intensive endeavour due to the high capital cost of acquiring or constructing the furnaces that are required for the process. In addition, such boronizing facilities have high operational costs associated with the operation of the furnaces.
SUMMARY OF THE INVENTION
What is required is a less costly method for boronizing a workpiece.
According to the present invention there is provided a method for boronizing a metal workpiece which includes the following steps. A container is provided having a least one workpiece receiving chamber and at least one heating chamber adapted to heat the workpiece receiving chamber. The metal workpiece to be boronized is placed within the workpiece receiving chamber in physical contact with a boronizing agent. The heating chamber is heated until the workpiece receiving chamber is heated to a sufficient temperature for a sufficient length of time to boronize the workpiece.
With the method, as described above, an internal heating chamber positioned within the container is used to supply heat for the boronizing process, as opposed to placing the container into a boronizing furnace. This eliminates the need for a boronizing furnace, with all of its associated expense. Once the basic teaching of the method is understood, the container can be made in various ways. The workpiece receiving chamber is made to accommodate the geometry of the work pieces being boronized. There are various means for heating the internal cavity of the container. The embodiment hereinafter described is for purposes of illustration only.
According to another aspect of the invention there is provided an apparatus for boronizing a metal workpiece which includes a male housing and a female housing. The male housing contains a heating chamber. The female housing has a sidewall defining an internal cavity. The male housing is insertable into the interior cavity of the female housing to form an annular workpiece receiving chamber between the male housing and the sidewall of female housing. In the embodiment which will hereinafter be described an internal heat source is disposed within the heating chamber. It will be appreciated that the heat source could be external to the apparatus and merely channel heat into the heating chamber.
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Boronizing, Alfred Graf von Matuschka, Carl hanser Verlag Munchen Wien, 1980, pp. 44-49, along with page containing bibliographic information and page containing table of contents.
Foster Gerald Allen
MacKenzie Dale William
Christensen O'Connor Johnson & Kindness PLLC
Lund Jeffrie R.
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