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mardi 24 novembre 2015

Useful Facts About Diffusion Coatings

By Marci Nielsen


Metal components are meant to be used or operated in different environments. Some of those environments are very harsh in that they have very high temperatures, are very corrosive, or are very reactive among other conditions. Such environments are able to cause very severe effects when they come in contact with metal components, which may lead to a significant reduction in durability, aesthetic value, and functionality among others. To curb the effects of such environments, diffusion coatings were invented.

Diffusion coating is the process through which metal substrates are coated with diffusion coating. The process requires a special piece of equipment called a chamber and optimal temperatures are usually very high. Thorough cleaning of substrate must be done first before the process is started. Abrasive blasting is the most commonly used method although other methods can be used. Unwanted materials must be removed because they prevent complete bonding between the metal and substrate.

Once the substrate has been cleaned properly, it is placed into a contained together with the metal used for coating. The container is then placed inside a furnace or a chamber. The furnace is turned on and the temperature set to the range of 380-425 degrees centigrade.

At those temperatures, the diffusion of the metal occurs, which allows it to form an alloy with the substrate or component. This process lasts variable amounts of time depending on the metal used and the nature of the substrate. Typically, it lasts between two to four hours. During the entire time, the component is rotated slowly for a uniform coating to form.

The resultant coating is smooth and its thickness is very uniform. Depending on the function of a component, the thickness can be varied. However, the normal range of thicknesses is between 15-80 micrometers. The color of the metal used for coating forms the color of the component after coating. Chromium, iron, aluminium, and silicon are among the most commonly used metals. Coating can also be done to various metals too, including iron, steels, cobalt, and nickel.

The coating is resistant to erosion, oxidation, and reaction with air, water, and other substances. A lot of reliability, durability, and strength is achieved in components that are needed in critical functions. Pump impellers, power generation constituents, gave valves, and components or gas turbines engine like vanes, blades, and cases are examples of parts that usually get coated through this method.

The use of this process is mostly confined in industrial settings. Very few household devices incorporate this process in their production. The invention of the process happened several years ago and it has been undergoing modification over time to achieve perfection. Currently, better methods and technology exist.

Modern day furnaces have a lot of improvements in the form of features aimed at increasing efficiency and functionality. Today it is possible to achieve very thin coatings that are very strong and effective at eliminating corrosion. The automotive industry is particularly known for using this technology.




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