Cemented Carbide Tool Wear

Cemented carbide tool wear is the phenomena, in high temperature conditions the tool material is gradually wear or breakage by the workpiece, the friction of the chips. Research tool wear causes prevent premature excessive tool wear and how to extend tool life, which is affecting the efficiency of production, processing costs and processing quality is an important topic.

Cemented carbide tool wear in the form of: Cemented carbide tool wear normal and abnormal tool wear can be divided into two categories. Normal tool wear the continuous gradual wear and tear, abnormal tool wear, including brittle breakage and plastic damaged two.

1. Normal cemented carbide tool wear: increase wear gradually expanded form, including wear in front of the main flank wear, vice flank wear with cutting time.

2. Abnormal cemented carbide tool wear, also known as broken

(1) the groove wear: depicts different shades of the groove in the tool behind. This is mainly due to the wear resistance of the tool material is not enough, or the material surface due to hard spots friction.

(2) The cemented carbide tool cutting edge small gap: on the cutting edge of particle shedding forming irregular tiny gap, which is increased brittleness due to high blade hardness sharp cemented carbide tool cutting edge strength deterioration, damage the cause of the intermittent cutting or chips.

(3) Plastic deformation: the cemented carbide tool cutting area due to a severe plastic deformation around the flank and cutting edge collapse, caused mainly, cutting temperature and cutting too much pressure, head strength and hardness decreased. Especially high-speed steel tools prone to this form of cemented carbide tool wear.

(4)The cutting edge by the greater impact force to crack: the cutting edge and rake face, back to eat knife ɑp and the feed amount of ? the ambassador cutting force increases, are subject to the middle to cut the main vice cutting edge cutting force, the rake angle is large and the low intensity of the situation caused by a large area of the cemented carbide tool cutting edge and rake face crack.

(5) Cutting edge peeling: Flank or cutting edge around the surface off and damage the tool, such damage often occurs in the high hardness and brittleness of ceramic tool. And in the case of larger pressure and friction is easy to produce.

(6) Heat cracking: in a direction perpendicular to the cutting edge due to the heat cracks. Thermal cycling causes material fatigue from, or due to intermittent cutting and cutting fluid pouring uneven cutting sudden changes in temperature, easy to cause the flank face minor cracks before.

Cemented carbide tool wear mechanism:

1. The abrasive wear: the presence of oxides, carbides and nitrides and other hard particles in the workpiece material. In cast, forgers member on the surface of the existence of hard inclusions and adhered on the surface of the chips, processing hard BUE fragments, these hard particles during cutting to match the "abrasive" the role of the surface friction of the tool and characterization resulting in cutting edge flank wear. The abrasive wear is a mechanical friction nature of cemented carbide tool wear.

2. Phase change by abrasion: the tool steel cutting tool at higher speeds, the cutting temperature, so that the tool material generates phase change, hardness decreased, and if the continue cutting, it will cause the front of collapse and the cutting edge is curled. Cemented carbide tool at high temperatures (> 900 ° C), a high pressure state where cutting will produce plastic deformation and losing machinability.

3. Adhesive wear: Also known as cold welding wear. When the tool materials and workpiece material are bonding, the relative movement between the bonding point shear failures, due to the tool materials bonded particles away. Changes in material properties of the surface layer in the high temperature and high pressure under the action of the tool, when the workpiece and the tool to produce relative movement, the tool material bonded particles are taken away to form an adhesive wear.

4. The diffusion wear: high temperature, so that the workpiece and tool material interdiffusion of alloying elements replacement caused.

5. The oxidation wear: also known as border wear, cemented carbide tool cutting temperature of 700-800 ℃, carbide material WC, TiC and as Co and air oxygen starting compounds, the formation of a low hardness and strength oxide film. By cutting the workpiece surface oxide skin, the chilled layer and the hard impurities point continuous friction, causing the oxide film to be processed at the surface of the knife surface oxidation wear.

Reasonable choice of tool material, tool geometry parameters, can improve tool wear resistance, heat resistance and chemical stability. In addition, the increase tool strength and tool sharpening quality to improve the cooling conditions, the rational use of cutting fluid, can effectively prevent cemented carbide tool wear.

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