Metal treatment – Stock – Amorphous – i.e. – glassy
Reexamination Certificate
1998-10-16
2003-08-19
Wyszomierski, George (Department: 1742)
Metal treatment
Stock
Amorphous, i.e., glassy
C148S408000, C148S409000, C428S678000
Reexamination Certificate
active
06607614
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to certain novel amorphous non-laminar phosphorous alloys, and, in particular, relates to amorphous non-laminar nickel phosphorous, amorphous non-laminar cobalt phosphorous and amorphous non-laminar nickel cobalt phosphorous alloys.
BACKGROUND OF THE INVENTION
Articles and devices formed from metal or having metal surfaces or coatings thereon have numerous applications and have found widespread use in a variety of industries. Depending upon the intended end-use of the metal article or metal-coated article, it is desirable that the surface metal exhibit a particular property or combination of properties.
Metal surfaces having properties such as lubricity, wear-resistance and corrosion resistance are desirable for a number of applications, such as molds and molding inserts. However, it is often difficult to achieve this combination of properties in the same metal surface. For example, electroplating an article with hard chrome imparts wear resistance and corrosion resistance to the article. However, an electroplated hard chrome article is time consuming to manufacture, requiring polishing steps prior to and after the electroplating step. In addition to these two polishing steps, when the substrate or article to be coated is hardened steel, the hardened steel must be subjected to a heat treatment step.
Further, the fabrication of high precision devices such as photographic and instrument lenses (Fresnel lenses, lenticular and rotogravure cylinders) as well as molds for optical products and information storage disks, requires that the device or the surface of the device be formed of a material which is very hard (to resist scratching), chemically inert in its ordinary environment (to prevent rusting, oxidation or tarnish which renders the surface unacceptable), and of suitable metallurgical purity (of a highly regular and dense-grain structure-free of slag, impurities, voids, or other unacceptable microflaws).
Initially, these high precision devices were commonly made of a monolithic metal such as aluminum, copper and certain grades of stainless steel and were fabricated in all the usual ways well known to the metal working industry, including metal removal via milling, grinding, lathe turning, fly cutting, or spark erosion by electrical discharge. Once the nominal dimensions, shape or contour of the fabricated device had been attained, the surface of the device was abrasively lapped by successively finer abrasives in a manner well known to those skilled in the art until the contoured surfaces reached satisfactory degrees of smoothness and polish.
More recently, in order to obtain the precision needed, the surface of the device has been machined by a technique known as single-point diamond turning. Single-point diamond turning is accomplished by taking a diamond crystal of the desired size and shape and combining with high precision machines, that may utilize either liquid or gas bearings in controlled environmental conditions, to produce superior quality optical components. This technology is an improvement over the above-mentioned methods that involve grinding, machining and polishing. Those methods are very time consuming, labor intensive and can lead to defects such as deformation and aberrations in the device surface. With diamond turning the tool is so hard and sharp that when very thin layers are cut into certain materials there is minimal edge contact and stress and friction applied to the material are at an absolute minimum. This results in a specular finish and a contour that is an exact replica of the tool path.
A problem with single-point diamond turning is the rapidity with which the diamond turning tool wears out. In addition, although this method of producing precision tooled devices works well, the number of materials with which is it compatible are limited. The materials that have found wide spread existence in the industry today mostly include but are not limited to aluminum, copper, certain grades of stainless steel and electroless nickel/phosphorous alloy.
Although aluminum and copper seem to produce acceptable results, both metals have a microcrystalline grain structure which makes it harder to attain the required surface finish. Both metals are also very soft which makes them susceptible to damage at the slightest contact. Both metals are also very reactive which can lead to severe corrosion even in the mildest of environments.
Stainless steels also have the same crystalline structure problems and because of the is hardness of this material, along with the crystal structure, causes the degradation of the diamond tool very quickly and is difficult and time consuming to polish.
High phosphorous electroless nickel deposits (≧11%) on a base metal substrate gives a surface which seems to have all the desired characteristics for a superior diamond turning material. They are reported as being completely amorphous in structure (no crystalline or grain structure discernible at 150,000×), have reasonable hardness (48-52 Rc) and a natural lubricity or low coefficient of friction that extends diamond tool life. The draw backs of this deposit are with the method, expense and limitations of the deposition process. (The solution chemistry is fairly expensive and at times can be hard to control as the reaction mechanisms are very complex and still to this day are not fully understood.) In addition, high phosphorous electroless nickel deposits typically contain 10-11.5% phosphorous content, with a maximum of 13% being claimed. Nickel/phosphorous alloys having a phosphorous content of between about 11% and about 13% can become slightly magnetic when exposed to temperatures in the range of 250° C. and 300° C. Such temperatures are typically encountered in the manufacture of memory disks. Therefore, memory disks manufactured using nickel/phosphorous alloys having a phosphorous content of between about 11% and about 13% may become slightly magnetic during the manufacturing process and must be rejected. Moreover, because the deposit is laminar in structure, the deposit quality varies greatly with varying layers containing different amounts of phosphorous. This results in a tendency for “banding” or demarcation lines to appear after diamond turning. This can be caused by solution chemistry imbalance (wetting and dispersion agents) and because of the slow deposition rate (0.0002″-0.0005″ per hr.). The slow deposition rate also makes it difficult to keep particulate matter out of the solution during the lengthy time required to deposit the nickel/phosphorous alloy to a suitable thickness. Particulate matter can co-deposit with the alloy, thus introducing impurities into the coating and causing a tendency toward the generation of pits and inclusions. The pretreatment cycle for most materials also has to be perfect as the operating solution has a pH that is close to neutral and does not offer any cleaning or oxide removal help the moment before deposition starts. Also because of the above problems and the tendency for the solution to want to plate the related process equipment it is very difficult to obtain high quality deposits over (0.008″-0.010″ thick. In addition, it has also been found that electroless nickel deposits may contain discrete cites of crystalline structures which are problematic for diamond turning applications.
For this reason, it has been suggested that an improved mold for optical thermoplastic high-pressure molding can be prepared by electroplating a relatively thick layer of nickel or chromium onto a beryllium-copper alloy substrate of certain specified mechanical and thermal characteristics. Thus, in Maus U.S. Pat. No. 4,793,953, there is disclosed a most preferred mold element construction that consists of, first, a machined beryllium-copper substrate onto which a thick Watts nickel plating was deposited, followed by abrasive lapping to create the specified surface contour to a high level of microstructure perfection and smoothness, onto which a final hardcasting of either va
Brockman Daniel A.
Richardson Rick Alan
Killworth, Gottman Hagan & Schaeff, L.L.P.
Techmetals, Inc.
Wyszomierski George
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