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What Is A Tool Coating System?

June 1st, 2012

Coating systems are chemical treatments used on machine cutting tools. Cutting tools can be extremely expensive and they wear down over time. Machine shops have always tried to find unique ways to increase the life of their tools and coating systems have been the number one way to do this. 

Coating systems can greatly increase the longevity of the tool. They can also help with lubricant cost, volume heat buildup, increasing shelf life, dimensional control and lubricity. Even a very thin layer of coating can make a large difference in the performance and life of a tool. It is for this reason that machine tool shops invest a lot of money into the research and selection of a coating system.

Now, the best solution for a tool coating system depends on the application or work material. What is the tool being used for? How is it being worn down? What surfaces does the tool perform edge grinding or shaping on?

Tools just get worn out over time due to friction. The metals (or work material) the tools cut or shape have an effect on the tool. It all depends on how hard the metal is and other factors, but it's only a matter of time before a tool is unusable. This is known as surface wear.

There are two major categories of surface wear: adhesive wear and abrasive wear.

Adhesive wear, also known as galling, is when two metals bond together, or adhere to each other. Galling is caused by a rough surface finish as well as the natural way that like materials bond together. Adhesive wear happens because metals aren't really smooth despite their appearance to the human eye. At the microscopic level, there are tons of ridges and valleys that jut out at sharp angles. As the tool comes in contact with the part it is shaping, tiny particles from the work material stick to those imperfections on the tool's surface. These eventually build up to where we can see them and soon the tool is rendered unusable, or at least can't perform the job up to standards.

Abrasive wear is when particles in the work material bang into or go through the surface of the tool. The particles are known as carbides and they'll scratch the tool up, cause craters and otherwise deform the surface of the tool over time. The carbides are harder than the metal of the tool and so "win out" over the tool's surface. 

Coating systems minimize both abrasive wear and adhesive wear. In both cases, the tool coating makes the tool's surface much harder and therefore less penetrable by other metals.

Tool coatings also typically have less friction than the hardened steel of a tool. Less friction equals less wear on the tool as well. Remember what we said about abrasive wear eating away at scratches or imperfections at the microscopic level? Well, usually a thin-film coating doesn't cover up those imperfections. So tools are first covered in a "mirror-finish" to smooth everything out first, and then the thin-film hard coating is applied to the tool - leaving it ultra strong and very resistant to all forms of wear.

Of course, different coatings are used for different applications. Just for example there is titanium carbide (TiC) or titanium nitride (TiN). There is TiAIN - X, Super-R Coating, Zirconium Nitride Coating (ZrN), and many more types. They are all applied in different ways and they all have different characteristics. The best one to use for a tool all depends on what sort of material you're grinding or shaping.

In summation, friction is bad and causes wear and tear on expensive machine cutting tools. Coating systems can greatly reduce the cost and degradation of those tools.

 

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This is the original version of this article that has been syndicated at places like Ezinearticles.com. 

Author: Julian Crain.