Cobalt/chromium alloys processing

The second approach, that of surface coating, is more difficult, and that means more expensive. But it is often worth it. Hard, corrosion resistant layers of alloys rich in tungsten, cobalt, chromium or nickel can be sprayed onto surfaces, but a refinishing process is almost always necessary to restore the dimensional tolerances. Hard ceramic coatings such as AbO, Cr203, TiC, or TiN can be deposited by plasma methods and these not only give wear resistance but resistance to oxidation and... 

In recent years, the spraying process has been adapted for hard facing, using the chromium-nickel-boron alloys which have become known as Colmonoy. More recently still, the cobalt-base Stellite alloys have also been used. These materials in powder form are sprayed on to the surface in the usual way. The deposit is afterwards heat treated by a torch, so that fusion takes place. The process is often known as spray-welding. Such coatings are primarily used for hard facing under wear conditions, but as the Anal surface is nickel-chromium or cobalt-chromium they exhibit very high anticorrosive properties. 

Polymer Solutions Incorporated received a molded silicone medical part that contained a small discoloration on the tip. It was of interest to identify the composition of this defect region in order to discover its origin. Testing showed that the defect was composed of an alloy of cobalt, chromium, and molybdenum, embedded in a silicone matrix. This alloy was present in another process in the same manufacturing facility and contaminated the silicone part. 

The preparation of the Raney-Ni catalysts follows the conventional method [14], Pure metallic cobalt, chromium, iron, and molybdenum as fine powders were added to nickel and aluminum powders, with a Ni/Me molar ratio around 0.02. Then, the alloy powders were submitted to a leaching process with soda under different temperatures to obtain promoted Raney-Ni catalysts. Besides the prepared samples, a commercial Raney-Ni catalyst (GETEC) was also tested [15], The industrial leaching process from GETEC was adopted sodium hydroxide solution (6 M) was added to the alloy and the mixture was heated at 100 and 120 °C for 2 h and stirred at 1200 rpm. 

Selective leaching is the removal of one element from a solid alloy by corrosion processes. The most common example is the selective removal of zinc in brass alloys (dezincification). Similar processes occur in other alloy systems in which aluminum, iron, cobalt, chromium, and other elements are removed. 

Electroplated Metals and Alloys. The metals electroplated on a commercial scale from specially formulated aqueous solutions iaclude cadmium, chromium, cobalt, copper, gold, iadium, iron, lead, nickel, platinum-group metals, silver, tin, and ziac. Although it is possible to electroplate some metals, such as aluminum, from nonaqueous solutions as well as some from molten salt baths, these processes appear to have achieved Httie commercial significance. 

The composition of the codeposition bath is defined not only by the concentration and type of electrolyte used for depositing the matrix metal, but also by the particle loading in suspension, the pH, the temperature, and the additives used. A variety of electrolytes have been used for the electrocodeposition process including simple metal sulfate or acidic metal sulfate baths to form a metal matrix of copper, iron, nickel, cobalt, or chromium, or their alloys. Deposition of a nickel matrix has also been conducted using a Watts bath which consists of nickel sulfate, nickel chloride and boric acid, and electrolyte baths based on nickel fluoborate or nickel sulfamate. Although many of the bath chemistries used provide high current efficiency, the effect of hydrogen evolution on electrocodeposition is not discussed in the literature. 

Pure nickel was first isolated in 1751. Like cobalt, nickel was used to color glass, though nickel compounds turn glass and other substances green rather than blue. Because nickel is resistant to corrosion, it is often combined with other metals to form alloys that resist oxidation. A process known as electroplating uses nickel to coat the surface of metals that are vulnerable to corrosion, like iron or steel. Stainless steel is an example of a product made from nickel almost half the nickel that is mined each year is used to manufacture it. Also composed of chromium, stainless steel is extremely resistant to corrosion. Another nickel alloy is monel, which is made with copper. Monel is hard and resistant to corrosion, making it ideal for commercial marine applications such as the manufacture of boat propellers. The heating parts in toasters and electric ovens are made from an alloy called nichrome, which is another metal, made from chromium and nickel. 

INMETCO s High Temperature Metals Recovery process reclaims the nickel, chromium, iron, molybdenum and cobalt fi om the secondary wastes indicated above and produces a remelt alloy in cast pig form, weighing 25-30 pounds. The remelt alloy is shipped to most of the stainless steel manufacturers in the United States, as well as certain other international companies, for use as raw material feedstock in the production of more stainless steel. As an ISO 9002 certified facility, INMETCO, a fully permitted facility, is the only High Temperature Metals Recovery facility in North America dedicated to the recovery of nickel, chromium, iron and molybdenum from both hazardous and non-hazardous wastes. 

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