The selection of carbide grade on the cemented carbide blade material is based on different addresses and different functions of the cemented carbide blade.

Cemented carbide blades have the characteristics of  high precision and high wear resistance and  has been widely used. According to the different uses of the product, cemented carbide blades can be divided into the wood cutting tools, clamping blade, milling and turning blades.

The most important part of a dart is the stem, it’s where fingers hold on. The change of stems’ weight will change the shape of darts. Nowadays standard dart stem is made from tungsten alloy and this kind of dart is getting more and more popular all over the world.

There are several kinds of tungsten alloy dart stems including tungsten-nickel-copper stem, tungsten-nickel-copper-iron stem etc. If customers need special darts, they will be customized. Since there are still some barriers in manufacturing skills, tungsten dart stems with purity of 100% can not be made yet. What people can buy in the market are almost tungsten alloy stem, among which tungsten-nickel-iron alloy is the most common one.

Tungsten is a kind of material with high density and endurance. Tungsten alloy dart has small diameter compared with dart made of other materials at the same weight. For dart fans, small-size stem is very important, for it’s more comfortable to hold with fingers. The advent of tungsten alloy darts has contributed a lot to dart sports, as it has greatly improve the average scores in games.

There are some tips for dart fans:

1. When you buy a new set of darts you may notice the percentage of tungsten in the package, say, “tungsten purity 80%”, that means 80% of the material in the stem is tungsten, and the higher the purity the thinner the stem is and, of course, the more expensive the darts are. For ordinary fans 80% is good enough.

2. Remember: the only advantage of a high-purity tungsten alloy dart is that it is thinner, it does not mean it’s of high quality or fine workmanship.

3. Some people are allergic to nickel, and nickel happens to be an element of some darts stem, if those people really want to play dart, they’d better chose a substitute, like tungsten -copper darts.

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Cemented carbide  is made by the chemical vapor deposition (CVD) method,which coats TiC or TiN, HfN, Al2O3, and other wear-resistant on the surface of the carbide alloy inserts,so that the carbide alloy coating is formed. This is an important progress of modern cemented carbide  researches. The Sidek Krupp and the Swedish Sandvik company had developed TiC coated carbide inserts and put it into the market for the first time in 1969. After 1970, the United States, Japan and other countries were beginning to produce this  kind of blade. For more than thirty years, the coating technology has made great progress. Coated carbide blade has been developed from the first generation, the second generation to the third generation, fourth generation products.

                  
The advantages of cemented carbide coating:
1) coated cemented carbide  can  use the high cutting speed, thereby improving the processing efficiency;

2) since the smaller coefficient of friction between the coating material and the  processing material ,compared with uncoated blades, the cutting force of the coating blade has a certain decrease;

3) when the processing of the coating blade, the quality of processed surface  is excellent;

4) due to the good overall performance, coated blades have good versatilities. One coating grades of the blade can be widely used.

 

Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
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The key characteristics of CVD tungsten carbide coatings are as follows:

1、Outstanding chemical and corrosion resistance
2、Free from through porosity, thus effectively protecting mild steel substrate from corrosive media without sealing the coating
3、Superior resistance to sulfide stress cracking
4、Provides effective protection against mineral acids such as sulfuric acid and hydrochloric acid
5、Resists Aqua Regia at room temperature
6、Superior wear resistance; Wear rate of CVD tungsten carbide coatings is four fold lower when compared to thermal spray WC, 12 fold lower than hard chrome, and 40 fold lower when compared to abrasion resistant steel AR-500
7、Demonstrates better erosion rate when compared to chrome carbide weld overlay, hard chrome, white iron, cemented carbide, and various other hard materials
8、Better fatigue resistance and toughness
9、Superior resistance to impact and deformations
10、Deposition from the gas phase enables coating of internal surfaces and intricate shapes.

A micro-photograph of a cross-section of 50-microns thick CVD Tungsten Carbide coating type T on thread. The uniform coating follows the substrate; even slight imperfections are accurately followed (magnify. 20X).

Comparison results of ASTM G65 tests of CVD tungsten carbide coating abrasion resistance against other hard materials is depicted.

Results of ASTM G65 tests of CVD Tungsten Carbide coating abrasion resistance as compared to the results for other hard materials.

Corrosion resistance of CVD tungsten carbide coatings is demonstrated.

Samples of three different coatings after salt spray corrosion tests: left - HVOF after 480 hours; centre – Hard Chrome after 288 hours; right – CVD coating type T after 480 hours.
Applications of CVD Tungsten Carbide Coatings

CVD tungsten carbide coating is suitable for applications with many different components operating in extreme erosive and abrasive atmospheres, such as critical components of metal seated ball valves, downhole tools, and pumps handling abrasive fluids.

Ball valves coated with CVD tungsten carbide coating, demonstrate increased valve life thanks to the coating as it make them scratch-proof and able to resist erosion and abrasion.

Ball valves coated with CVD Tungsten Carbide coating.

CVD tungsten carbide coating extends the life and reduces downtime costs of downhole tools such as grippers for down-hole tractors, high loading bearings pins, and mud-driven hydraulic parts for directional drilling tools.

CVD tungsten carbide coating type T is applied on outside piston and inside cylinder of a positive displacement pump transporting abrasive viscous fluids at pressures as high as 2800 psi to reduce wear, thus increasing pump life threefold.

CVD tungsten carbide coating is an ideal alternative to phase-out hard chrome plating because it involves carcinogenic hexavalent chromium, thus causing negative impact on environment, health and safety.
Conclusion

With these qualities, CVD tungsten carbide coating becomes an ideal solution to improve the performance and life of critical components of valves, downhole tools, and pumps operating in power generation, cryogenic equipment, refineries, food manufacturing, and oil and gas facilities.
About Hardide Coatings

Hardide Coatings produce a range of advanced surface engineering coatings that protect the internal and external surfaces of components from wear, erosion and acidic corrosion.

The coatings are proven to extend the life of metal parts operating in harsh environments for a variety of industries including oil & gas, valves, pumps, aerospace and advanced engineering.

Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
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