What is the substrate?

A substrate is the raw material of the cutting insert before coating and post-treatment. It is often composed of 80-90% of WC - a combination of tungsten ( W) and Carbon(C). Manufacturers add various alloys and elements like Cobalt( Co) which increases the toughness of the substrate.   

Keeping cobalt percentage between 5-15% makes the substate harder, which is the primary property of the substrate. However, the toughness of the substrate is essential, too, and creating a balance with hardness is a tricky chemical combination. Grading the toughness of a substrate too high leads to micro breakage of the cutting edge.  

The hardness of a substrate at 1800HV makes it excellent to wear resistance but brittle and can only work in stable conditions. For toughness, the substrate required 1300HV for the cutting edge. 

What are carbide coatings?

Carbide is a compound made of carbon combined with less electronegative like metal or metal oxide. Some examples of carbide include; tungsten carbide or calcium carbide.  

Carbide coatings used in machining include;

Tungsten carbide coating

Tungesten carbide coating is typlly a fine grey powder in its basic form. When combined with a small portion of metallic powder (typically Co, Cr, or Ni), it can be turned into carbide coatings known for strong resistance to abrasion, erosion, and wear. 

The most widely used tungsten carbide coating is WC-Co after WC-10Co-4Cr. HVAF and HVOF tungsten carbide coatings have excellent resistance to sliding wear, abrasion, and erosion despite lower corrosion resistance than WCCoCr. 

Tungsten carbide coating is used to create tools for machining. The carbide substrate is commonly used when steel would wear down fast, with high production or precision.  

Chrome carbide coating

Chrome carbide is a hard-refractory compound with thermal stability and superior corrosion resistance. Chrome carbide coating applies to materials requiring high temperature and wear. 

Some of the properties of chrome carbide coatings includes;

• Excellent high temperature wears resistance.
• High bond strength
• Good corrosion resistance due to the formation of passive Cr2O3 and NiO2 layer from Chromium-Nickel matrix
• Superior strength

Other carbide substrate coatings are composed of compounds like aluminum oxide, titanium carbon nitride, and titanium nitride layers. The coating creates a heat barrier between the cut and the substrate. Two technologies adding coatings to cutting tools; 

• Physical Vapor Deposition ( PVD ) PVD coatings can range in thickness from 1 to 8 microns. PVD-coated inserts are designed to operate at lower cutting speeds; however, they are more challenging, can be applied on sharp cutting edges, and have smoother surfaces that generate less friction.
• Chemical Vapor Deposition ( CVD ) - CVD thickness can go up to 25 microns, ensuring an effective heat barrier that enables a higher cutting speed than PVP coatings. The same thickness makes cutting edge impossible, making the coating prone to cracks and brokerage.  

Are there different grades of carbide?

Choosing the grade for carbide depends on the tools you are applying the substrate for. For instance, a 05 application requires a tough grade suitable for favorable and stable conditions, while a 45 application needs a tougher grade suitable for unstable conditions.   

Carbide grading durability comes in several ranges from C1 to C17 and has different degrees of resistance. The grading degree applied depends on the tool’s application. Is it the material being cut or drilled?

C2 carbide is used for milling tools where the temperature does not exceed 400 degrees Celsius. The carbide will decompose if the temperature exceeds the mark. During roughing, C2 grading is used for metals like aluminum. 

If you have any questions about carbide cutting tools, end mills, drills, etc. be sure to reach out to us @ sctools.co/Home or call us at (877)737-0987. We help you machine better!