Carbide tool wear problem

Carbide is a material with high hardness, high wear resistance, high strength and high chemical stability. However, it will still suffer from various kinds of wear during use, eventually leading to failure. In this article, we will discuss this problem by 4 parts:

1. What is the cause of carbide tool wear?

2. What are the different types of tool wear that occur in a cutting tool?

3. What are the stages of tool wear?

4. How to prevent carbide tool wear?

 

cutting tool wear

 

1. What is the cause of carbide tool wear?

 

1) Hardpoint wear is the main cause of carbide tool wear

 

(1) The main causes of hard point wear are as follows:

 

a. The role of cutting force:

 

Hardpoint wear is mainly caused by cutting loss, and cutting force is the direct cause of cutting loss. The greater the cutting force, the more obvious the hard point wear is.

 

b. Interference of work materials:

 

When processing brittle materials such as hard films and ceramics, abrasive particles are easily stuck in the gaps on the material surface, causing wear of hard points on the cutting surface.

 

c. Surface structure and composition:

 

The degree of wear of hard points has a great relationship with the structure and composition of hard points. Generally speaking, hard points with small grains, few twins, and uniform composition are not easy to wear.

 

(2) Solutions to hard point wear

 

a. Change the hard point structure

 

The wear of hard points can be reduced by using hard points with special shapes, special compositions and structures such as nanocrystals.

 

b. Change process parameters

 

By adjusting process parameters such as tool cutting speed, feed speed and cutting angle, hard point wear can be reduced.

 

c. Use tool coating

 

Surface modification of carbide tools and coating with titanium alloy, molybdenum alloy or other compounds can effectively prevent hard point wear.

 

2) Defects in the material itself

 

Common defects in carbide-cutting tools are elongated inclusions, bubbles, inhomogeneities and twins. These will become the weaknesses of carbide tools and easily cause damage during the cutting process. Therefore, choosing carbide tools made of raw materials with high purity and appropriate proportions can effectively reduce wear.

 

3) Improper processing technology

 

During the processing of carbide tools, improper handling of various processes such as sintering, polishing, coating, etc. will cause surface or internal defects of the carbide tools, thereby affecting the wear of the tools.

 

4) Cutting friction

 

The friction caused by long-term contact between carbide tools and workpieces will cause surface wear of carbide tools and accelerate the shortening of tool life. Cutting parameters that are too large or too small can also cause tool damage. For example, cutting too fast will cause excessive tool wear.

2. What are the different types of tool wear that occur in a cutting tool?

 

Serious wear of cemented carbide tools will cause difficulty in regrinding and affect the processing quality of precision parts. Due to different workpiece materials and different cutting materials, the normal wear of carbide tools has the following three situations:

 

1) Flank surface wear

 

The flank wear only occurs mainly on the flank surface. After wear, an edge surface with αo ≤ 0o is formed, and its height VB represents the amount of wear. This kind of wear is generally caused by cutting brittle metals or cutting plastic metals at lower cutting speeds and smaller cutting thicknesses (αc < 0.1mm). occurs. At this time, the mechanical friction on the rake surface is small and the temperature is low, so the wear on the flank surface is greater.

 

2) Rake face wear

 

Rake face wear means that the wear part mainly occurs on the rake face. Generally, when cutting plastic metal at higher cutting speeds and larger cutting thickness (αc > 0.5mm), chips flow out from the rake face. Due to friction, high temperature and high pressure, they are ground out on the rake face near the cutting edge. Crescent crater. The amount of wear on the rake face is expressed by the crater depth KT. During the processing of precision parts, the craters gradually deepen and widen, and expand toward the cutting edge, even causing chipping.

 

3) The front and flank surfaces are worn simultaneously.

 

Simultaneous wear of the front and flank surfaces refers to the simultaneous wear of the rake and flank surfaces on the carbide tool after cutting. This is a more common form of wear when cutting plastic metals at moderate cutting speeds and feeds.

The total cutting time from the time the carbide tool is sharpened and used for precision parts processing until the wear amount reaches the wear limit is called the carbide tool life, which is the pure cutting time between two regrindings of the carbide tool. Comprehensive, expressed in accordance with the “T”. If the wear limits are the same, the longer the service life of the carbide tool, the slower the wear of the carbide tool.

 

3. What are the stages of tool wear?

 

The wear process of cemented carbide tools is divided into three stages: initial wear, normal wear and severe wear.

 

1) Initial wear stage

 

When the carbide tool and the workpiece first come into contact, due to the large surface roughness of the newly sharpened tool, as well as defects such as micro cracks, oxidation or decarburization layers, the actual contact area is small and the contact points are seriously bonded, so the tool wears. Faster. As cutting progresses, the micro-peaks on the tool surface are gradually worn away, the surface roughness value decreases, the actual contact area increases and the number of contact points increases, so the wear rate of the carbide tool decreases. Coated carbide cutting tools wear more evenly at medium and low speeds. As the speed increases, the wear zone begins to take on a parabolic shape.

 

2) Normal wear and tear stage

 

After initial wear, the rough surface of the carbide tool is gradually smoothed and enters the normal wear stage. The wear at this stage is relatively slow and uniform, and the wear amount increases approximately proportionally with the increase of cutting time. This stage is the effective working stage of the tool. When the tool wear enters the normal wear stage, the wear area of the secondary flank surface shows uniform wear. Especially for coated carbide tools, the wear range shows uniform strip wear. Compared with uncoated carbide tools, its wear enters the normal wear stage more slowly.

 

3) Severe wear stage

 

When the wear amount of the carbide tool reaches a certain value, the cutting force will increase sharply, the cutting temperature will also increase rapidly, the flank wear value will increase significantly, the mechanical efficiency will decrease, the accuracy will be lost, abnormal vibration and noise will be generated, and finally cause The cutting performance of the tool decreases, eventually causing the carbide tool to lose its cutting ability.

 

4. How to prevent carbide tool wear?

 

1) Choose high-quality tools

 

High-quality carbide cutting tools have high wear resistance and can reduce wear during the cutting process. Choosing tools produced by manufacturers with strong technical platforms and high-quality manufacturing technology can effectively improve tool quality.

 

2) Correct use and maintenance

 

During use, strictly follow the usage requirements and operating procedures provided by the manufacturer to avoid usage errors and unnecessary wear and tear. At the same time, the cleaning, oiling, care and maintenance of cutting tools are also important measures to effectively extend the life of cutting tools.

 

3) Reasonable cutting parameters

 

In the process of using carbide cutting tools, it is necessary to set the cutting parameters reasonably and establish a reasonable cutting model. When determining cutting parameters, multiple factors such as workpiece material, hardness, tool material, and workpiece processing conditions need to be considered to achieve optimal cutting efficiency and avoid excessive wear caused by too large or too small cutting parameters.

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