Carbide Turning Tools
- October 15, 2020
- Cryogenic Processing
Cutting tools are essential in the machining process. The tools that are used for this specific purpose are different from other cutting tools like knives or punches. They mostly have industrial applications and are made out of specialized materials for more effective cutting power.
Cemented carbide is one of the most commonly used hard materials for manufacturing cutting tools that are to be used for industrial applications. These tools are made by cementing fine particles of carbide into a composite by a binder metal. Tungsten carbide and titanium carbide are the most commonly used cemented carbides.
What are carbide turning tools and how are they used?
The tools that make use of cemented composites on the tool head are called carbide turning tools. This hard material is used for its exceptional cutting properties. Carbide turning tools also leave a better surface finish on the material that they’re used on. They also allow for faster machining compared to high-speed steel or other tool steels.
These tools are capable of withstanding higher temperatures at the cutter-workpiece interface compared to standard tools. Carbide is also superior for cutting through tough materials like stainless steel or carbon steel. They’re very useful in situations, like high quantity production runs, where other cutting tools would wear much faster.
They’re meant to be used in a very specific manner because contrary to what most people might think, the entire tool isn’t made of carbide. That’s because carbide is more expensive per unit than other tool materials.
It’s also more brittle which makes it susceptible to chipping and breaking. These problems are offset by using a cutting tip made out of carbide that’s in the form of a small insert for a larger tipped tool.
The shank of the tool is made from another material that’s often carbon tool steel. This is done so that the benefits of carbide can be realized at the cutting interface without incurring the high cost or the brittleness of making the entire tool out of this expensive material. In modern face mills, carbide inserts are widely used.
Carbide tools are often coated in order to increase their life. The coatings may include titanium nitride, titanium carbide, and aluminium titanium nitride, among others. Diamond-like carbon is a newer coating that’s used to enable the cutting power of diamond while eliminating the risk of an unwanted chemical reaction between real diamond and iron.
These coatings generally increase the tool’s hardness and lubricity. Another way to significantly increase the lifespan of these tools is to use deep cryogenic treatment.
This is achieved by improving the resiliency of the cobalt alloy binding which holds the carbide-composite tools together, thereby resulting in a dramatic increase in the durability and tool life.
Which is better, HSS or carbide?
Carbide and high speed steel or HSS are two materials from which most cutting tools are made. Both have their own advantages so it really comes down to the specific use case to ascertain which particular material is better suited for the job.
High speed steel is a high carbon tool steel that has a significant amount of tungsten and cobalt. It’s rich in molybdenum, tungsten, and vanadium. They provide the tool with high hot hardness and high wear resistance.
These properties are achieved because of the special microstructure that makes the tool resilient to the high temperatures involved in high speed cutting.
Even after quenching and low temperature tempering, common carbon tool steel retains very high hardness at room temperature. A sharp reduction in hardness is seen when the temperature increases to a very significant level, resulting in a complete loss of cutting.
At temperatures above 900 fahrenheit, the tool can experience a sharp reduction in hardness. Therefore, HSS is primarily used to forge metal cutting tools, drill bits, hobs, machine saw blades, etc. Small and highly precise tools can also be created with it.
With carbide turning tools, it’s possible to machine even harder materials because they have a high red hardness. Even at temperatures beyond 1000 fahrenheit, the carbide turning tools will retain their high hardness.
A higher cutting speed can be achieved with carbide tools because of their heat tolerance, it can be up to seven times higher than that of HSS. Carbide is also much harder and this means that tools made from it have a longer life.
HSS tools tend to be less expensive than Carbide tools so they’re good for use in low-volume and high-mix applications. Carbide tools are perfect for jobs where temperature requirements are intense.
Deep cryogenic treatment of carbide turning tools
The process of deep cryogenic treatment involves submersion of the tool in a bath of cryogenic material like liquid nitrogen. This is done to rapidly bring down the temperature in order to alter the microstructure of the metal.
How it works
Deep cryogenic treatment has proven to be very effective for increasing the lifespan of carbide turning tools. That’s because it has shown to significantly alter the microstructure of tungsten carbide.
This causes the beta-phase particles to increase in size and quantity while a corresponding decrease is seen in the eta-phase and γ-phase particles.
Deep cryogenic processing has also shown to increase the hardness of cutting tools by about 7 percent. It’s essential to take the proper precautions with the tool after they have been treated. That’s because keeping the carbide cool is essential to maintaining the wear resistance that’s created by this treatment.
There isn’t a standard treatment method that can be applied to all carbide turning tools, though. In most applications, the specific tungsten carbide composition varies. This makes several trials necessary in order to determine the right protocols for the cryogenic treatment.
Learn more about carbide treatment
There are a number of studies that show the effectiveness of deep cryogenic treatment on carbide turning tools. A study conducted to determine the effect of cryogenic treatment on the performance of high speed stools and carbide inserts found that cryogenic treatments do increase tool life.
As part of the study, the tools were cryo-treated for 24 hours and then flank wear, sliding wear, and hardness tests were conducted. The cryogenically treated tool performed much better as it demonstrated an increase in tool life compared to HSS tools.
A separate study looked at the performance of non-treated and cryogenically treated carbide tipped drills at various levels of cutting speed, feed, and tool conditions.
The results were then analyzed using the ANOVA, SEM and Grey Taguchi relational method. It was found that cryogenically treated inserts demonstrated much superior results in terms of tool wear, reduced forces and the surface roughness of the drilled holes in comparison to non-treated tools.
We specialize in the deep cryogenic treatment of cutting tools at Controller Thermal Processing Cryogenics, having worked with many types of tungsten carbide cutters, drills, end mills, and other cutting tools.
Our proprietary process is used to bring the temperature of the metals being treated down to below -300⁰F. This is done to alter the crystalline structure in order to transform it into a more uniform and durable construct.
The changes in this structure then become permanent when the temperature of the metal is brought back up gradually.
CTP Cryogenics is a leader in the cryogenic processing industry with almost four decades of experience in serving a diverse range of clients that include the likes of NASA, the US Postal Service, and Remington Firearms.
We use state-of-the-art equipment and offer our services from three locations across the United States. Our services are available coast-to-coast.
Remember, the specific tungsten carbide composition varies so it’s important to determine the right protocols for the deep cryogenic treatment in order to avail the full benefit of this treatment.
We have ample experience in applying the perfect process for your exact carbide composition.
In case you’re curious about the deep cryogenic processing of cutting tools or would like any of your tungsten carbide parts to be treated, reach out to the team at CTP Cryogenics today for a free quote.