Making Cermet II Materials
What follows are some explanations of how to make advanced carbide. These are pretty short explanations but they will give an idea of all that is possible.
Obviously we use different techniques for different grades and applications. We have compiled a great deal of infomation on Carbide and Advanced Materials in our Tool Tipping Index. How It Works
Carbide wear is due to micro-fracturing, macro-fracturing, grain pull out, corrosion of the binder, adhesion between the carbide and the material being cut, and tribological functions which are similar to a naturally occurring electro-etching.
Cermet II technology uses a variety of carbides such a titanium carbide, tungsten carbide, Tantalum carbide, Niobium carbide and others. Steel is iron with a very small amount of carbide but it is very different than plain iron. The addition of a very small amount of the right material can make a huge difference in carbide performance as well.
Cermet II grades also use unique binder formulations. Cobalt is a good binder material and is used in standard grades. It was the first binder used and is still easiest to use. However cobalt is pure metal and is subject to chemical attack. Part of the secret of our Cermet II grades is to chemically alloy special binders with a proprietary metalloid which makes the cobalt binder non-reactive so it doesn’t corrode. It also greatly strengthens the binder so grinds aren’t pulled out.
Cermet II grades have special binder properties so that they behave more as a solid piece of material than as a cemented piece of material. Think of a steel alloy as compared to concrete.
Grain Size
The most important reason for this widening of the spectrum of available WC grades is that, besides those variations achieved by cobalt contents and some carbide additives, the properties of WC-Co hardmetals such as hardness, toughness, strength, modulus of elasticity, abrasion resistance and thermal conductivity can be widely varied by means of the WC grain size. While the spectrum of available WC grain sizes ranged from 2.0 to 5.0 µm in the early days of the hardmetal industry in the mid 1920’s, the grain sizes of WC powders now used in hardmetals range from 0.15 µm to 50 µm, or even 150 µm for some very special applications.
Grain Size
The history of tungsten carbide powder metallurgy, and especially that of the hardmetal industry, is characterized by a steadily widening range of available grain sizes for processing in the industry; while, at the same time, the grain size distribution for each grade of WC powder became narrower and narrower.
The most important reason for this widening of the spectrum of available WC grades is that, besides those variations achieved by cobalt contents and some carbide additives, the properties of WC-Co hardmetals such as hardness, toughness, strength, abrasion resistance and thermal conductivity can be widely varied by means of the WC grain size. While the spectrum of available WC grain sizes ranged from 2.0 to 5.0 µm in the early days of the hardmetal industry in the mid 1920’s, the grain sizes of WC powders now used in hardmetals range from 0.5 µm to 50 µm, or even 150 µm for some very special applications.
The first submicron hardmetals were launched on the market in the late 1970s and, since this time, the micro-structures of such hardmetals have become finer and finer. The main interest in hardmetals with such finer grain sizes derives from the understanding that hardness and wear resistance increase with decreasing WC grain size.
With optimum grade selection, sub micron grain size tungsten carbide can be sharpened to a razor edge without the inherent brittleness frequently associated with conventional carbide. Although not as shock-resistant as steel, carbide is extremely wear-resistant, with hardness equivalent to Rc 75-80. Blade life of at least 50X conventional blade steels can be expected if chipping and breakage is avoided.
Advanced Manufacturing Techniques
Better, cleaner powder has been achieved through improved solvent extraction in tungsten chemistry as well as new techniques in hydrogen reduction and carburization to improve the purity and uniformity of tungsten and tungsten carbide powder.
New powder milling, spray drying and sintering techniques have resulted in improved hardmetal properties and performance. Notably, the continuous improvement of vacuum sintering technology and, starting from the late 1980’s, hot isostatic pressure sintering (SinterHIP) led to new standards in hardmetal quality.
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