Additive (Co, Ni and Zr) effect on Ag-WC-C contacts experimental procedure -Ⅱis shown as following:

Sample 2
Preparation process is substantially the same to sample 1, except that:
Silver is 49.7g; additive Co powder is 0.3 g;
Sintering 4.5 hours (in the sintering furnace at a temperature of 840 ℃), and finally re-pressing at a pressure of 13.5T / Cm2.

Sample 3
Preparation process is substantially the same to sample 1, except that:
Silver is 49.7g; additive Ni powder is 0.3 g;
Sintering 4.5 hours (in the sintering furnace at a temperature of 800 ℃), and finally re- pressing at a pressure of 16.5T / Cm2.

Sample 3
Preparation process is substantially the same to sample 1, except that:
Silver, 49.7g; additive Zr powder, 0.3 g;
Sintering 5 hours (in a sintering furnace temperature at 750 ℃), and finally re- pressing at a pressure of 14T / Cm2.

 

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Preparation of Ag-WC-C contacts needs to use tungsten carbide powder and other powder as its raw material; the following is part knowledge of tungsten carbide powder.

Cubic WC1-X is used to represents W - C is a non-stoichiometric composition;
What represent W-C stoichiometric composition are: the hexagonal WC, the hexagonal W2C. At room temperature, only the Six-Party WC is stable.
The hexagonal WC cell structure is staggered triangular prismatic shape, which is Non-Centro symmetric structure, its lattice constant a = 2.916 × 10-10m (hexagonal, a = b), c = 2.844 × 10-10m. Nowadays, the main appliance of tungsten carbide is used to manufacture high-quality carbide, and it can also be used in contact material, metal coating, metal ceramics and other fields.

The lattice constant also known as the lattice parameters, referring to the length of a side of the unit cell, which have a direct contact with the combination of atoms, and it is an important basic parameters of the crystal structure, whose change may reflect changes of the composition in the crystal and status of the force.
Studies have shown that the mechanical property of tungsten carbide is not only related to its composition but the sintering process, and is also closely related to its microscopic crystalline structure. Currently, the preparations methods of tungsten carbide powder methods are:
(1) Tungsten powder is first prepared, and then adds carbon to make it carbonized to obtain tungsten carbide powder;
(2) Preparation of tungsten carbide powder from tungsten carbide compound.

However, both methods have common drawback is that both need a high carbonization temperature (1300 ~ 2000 ℃), the preparation process is complex, and it is costly, what is more, tungsten carbide prepared by this way is usually near-spherical. Using this kind of tungsten carbide powder to prepare plate-like strengthening tungsten carbide powder, there is a need to adopt a special sintering process to make the WC grain growth into a plate, and its orientation is not ideal.

 

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Additive (Co, Ni and Zr) effect on Ag-WC-C contacts experimental procedure is shown as below:
Experimental Materials:
(1) Silver powder, 51g
(2) A plate-like WC powder, 7.2g, its average length is 2-5um, its length-thickness ratio is 3-5
(3) Graphite powder, 1.44g, its average particle size is 2 ~ 50μm, its density is 2.2 ~ 2.3g / cm³

Experimental procedure:
Sample 1
1. Weigh the above materials and sieve them (100 mesh stainless steel mesh screen), then add WC powder, graphite powder to the blender, mix and stir to get mixing powder;
2. Prepare silver nitrate solution (dissolve silver powder fully in concentrated nitric acid);
3. Pour the silver nitrate solution into the reaction vessel, complex with ammonia until its PH = 10; add the mixing powder to the reaction vessel and stir it, to obtain a composite powder;
4. Keep stirring and pour reductant hydrazine hydrate in a way of liquid spraying through an atomization device into the reaction vessel, until it response adequately;
5. Clean composite powders with distilled water to neutral, dry then (in the dryer, at the temperature below 90 ℃), to obtain dry coating silver (plate- shape grain tungsten carbide, graphite) complex powder;
6. Cold-press the coating composite powder, and then under H2 atmosphere, sintering 3 hours (in the sintering furnace, at a temperature of 840 ℃), and finally re-press at a pressure of 15T / Cm2 for AgWC12C3 contacts .

 

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The flights on your tungsten darts are the most vulnerable part, and because of that they will need to be replace often. Let’s learn how to replace tungsten dart flight!

Instructions:

Choose your dart flights. Standard dart flights are pretty wide, which effects the movement of the dart. They straighten the dart out in the air, which makes them good beginner flights. They are also good for people who like to lob their darts rather than throw them straight with a lot of force. Narrower flights are good for short shaft darts and for aggressive throwers. Check the reference below for more info on dart flights.

Pull the old flight straight out of the shaft of your dart. You can save it in your dart case as a spare, or simply throw it out.

Inspect the dart shaft. If it is cracked or bent in any way, unscrew it and screw in a new shaft. Plastic shafts go bad all the time, and a new flight won't help your game if it is wobbling around in an old shaft.

Gently bend the new flight so that the planes are at right angles to each other. The flight should form two flat, intersecting planes for a total of four fins.

line up the flight with the slits on the back of the shaft. Gently push the flight into the shaft until it is all the way in.

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