The wear resistance of different particle sizes of tungsten carbide powder was compared and analyzed. The wear resistance of spray welding layer increased with the decrease of casting tungsten carbide particle size. The reason is: with the decrease of the particle size of cast tungsten carbide, its distribution in the spray welding layer is improved, and the microstructure of the spray welding layer becomes more uniform. On the contrary, the larger the cast tungsten carbide particles are, the larger the gap between them is, and the more easily the abrasive particles invade the base metal and wear it out. The casting tungsten carbide particles are widely spaced, and the scraping action of polygonal quartz sand edges and angles on the soft matrix phase on the surface of the spray welding layer will result in serious wear and tear of the matrix phase, and finally the hard phase particles will fall off due to the loss of the maintenance of the matrix phase. The cast tungsten carbide particles are small and the distance between the particles is small.

Casting tungsten carbide powderplays a key role in abrasion resistance during the process of wear and tear, and the shielding and protection of the softer matrix phase in turn leads to the matrix playing a good holding role relative to casting tungsten carbide alloy powder, so that it will not fall off. In this way, they rely on each other and play their respective roles.

Different kinds of tungsten carbide have great differences in hardness, toughness, cladding performance and so on. One or more mixtures can be reasonably selected as hard ceramic phases according to the working conditions.

Single crystal tungsten carbide can be prepared by mixing tungsten powder with carbon black in a high temperature carburizing furnace. The hardness and toughness of tungsten carbide are between cast tungsten carbide and sintered tungsten carbide. At the same time, it has good wetting property to iron group metals. However, the content of monocrystalline tungsten carbide in the surface composite material should not be too high, otherwise, the phenomenon of bridging monocrystalline tungsten carbide is extremely easy to occur, especially in the laser cladding process. The bonding force between the bridge surfaces is very weak, and it is easy to be damaged from the bridge surface under external load, resulting in spalling of tungsten carbide and reducing wear resistance.

Precautions for health protection of personnel in tungsten carbide powder production workshop

Due to the fact that tungsten carbide powder is a micro powder, the following matters should be noted by relevant personnel in the tungsten carbide powder production workshop:

1. Tungsten carbide dust can cause bronchitis, bronchiolitis, atresic bronchiolitis and atrophic emphysema.

2. Tungsten carbide can cause the proliferative reaction of lymphocytes in the lungs and gradually harden. The walls of the blood vessels thickened and homogenized.

3. Gastrointestinal dysfunction, renal irritation and catarrh inflammation of the upper respiratory tract occurred in people exposed to tungsten carbide dust at work.

Therefore, in the environment with access to tungsten carbide powder, it is necessary to use a gas mask, dust suit, gloves and glasses that meet the requirements. Tungsten carbide powder production in all stages to prevent dust leakage, workers to do pre-employment physical examination, a regular examination every year. When worker upper respiratory tract appears apparent symptom, want to transfer work temporarily, disengage from contact with tungsten. When appear lung sclerosis or outside respiratory function maladjusted, should transfer from the post.

Read more at wococarbide.com

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