General Carbide - Grade Selection Guide

Grade Selection Guide

Choosing the right carbide grade involves selecting a combination of materials to produce a grade that will give the best performance for a given application. The process starts by reviewing the specific application and trying to identify the likely failure mechanism.

Carbide grades can be custom-made by selecting from the following list of raw materials:

Cobalt in concentrations from 3% to 30%.
Nickel in concentrations from 6% to 15%.
Tungsten carbide in particle sizes from sub-micron to approximately 10 microns.

At General Carbide Corporation, we make a wide range of cobalt and nickel grades. Before we select specific grades for different applications, we first consider the following properties of carbide that are generally measured.

Hardness The hardness of cemented carbides is generally measured on the Rockwell A scale and reported as RA. For cemented carbides, the hardness will increase as the cobalt content and particle size of the tungsten carbide are decreased.

Density The density is measured as grams per cubic centimeter and is checked on each batch to insure the proper amount of cobalt was added. The density of cemented carbide will increase as the amount of binder is decreased.

Coercive Force This property measures the rate of decay of a magnetic field in the carbide. Coercive force values will increase as the binder and particle size of the tungsten carbide are decreased. Coercive force values for nickel grades are usually close to zero because of the low magnetic properties of nickel.

Magnetic Saturation This test determines the carbon potential of the powder lot and enables the metallurgist to determine how near a powder lot is to having eta phase or C-porosity after sintering.

Transverse Rupture Strength (TRS) This test gives the strength of the carbide as measured by a three-point bending test. The tensile strength of the carbide is approximately one-half of the TRS value. The transverse rupture strength of a cemented carbide can be increased by increasing the binder content and, in some cases, by decreasing the particle size of the tungsten carbide. This strength is measured in lbs/in² or N/mm².

Porosity Rating This test involves a visual examination of a polished surface at 200X. It is reported as "A" microporosity, "B" macroporosity, or "C" as free carbon in the microstructure.