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Corrosion Resistance on Tungsten Alloy Surface

Although tungsten alloy has high density cermet inserts and good mechanical property, properties of tungsten alloy surface such as poor wear resistance and corrosion resistance limit the applications in some aspects.

For that scientists do researches on handling tungsten alloy surface. Dini carried on chemical corrosion on tungsten alloy surface. Then a lay was electroplating deposited on tungsten alloy surface, improving anchoring strength between Ni and tungsten alloy surface so that improved the corrosion resistance on tungsten alloy surface. Eroglu, Ekren and Baykara hardened the surface of 92.5W-5.25Ni-2.25Fe directly in the atmosphere combining CH₄ and Ar, under the temperature of 1200℃.


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Internal Grinding Machine Features Four Spindles

The CT960 universal internal grinding machine from Studer features a fully interpolating B axis and four spindles for complex grinding tasks.

The CT960 universal internal grinding machine from United Grinding features a fully interpolating B axis and four spindles for complex grinding tasks. It is suitable for machining small- to medium-sized parts including die plates, spring collets, toolholding fixtures, hydraulic components, medical components and thread ring gages in materials including tool steel, tungsten carbide, ceramic and glass.

The grinding spindle turret features a dynamic direct drive said to enable faster swiveling times. Workpieces can be completely machined in the same clamping. The swiveling time is less than 2 sec. for 90 degrees, and less than 3 sec. for 270 degrees. The angular position of the grinding spindles is infinitely variable from -5 degrees to +30 degrees in all four positions. The automatic B axis of the workhead features a swiveling range of +61 to -91 degrees. The B axis has no contact surface, and is completely closed and virtually wear-free. A coolant distributor is designed to ensure well-regulated internal conditions.

 

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Tungsten Copper Electrode Infiltration II

Powder granularity: It stresses that tungsten powder granularity has an effect on tungsten copper electrode and other properties. Generally, the higher sintering temperature, the larger average granularity and the better strength of tungsten skeleton. However, if the granularity of tungsten powder exceeds a certain degree, the contact area among tungsten powder will be reduced and the tungsten powder can not be necking, which decreases the strength and hardness of tungsten skeleton and material.

Some scientists do some researches about tungsten powder granularity and volume fraction effects on density of tungsten copper electrode, they thought it depends on original grain size of tungsten powder and this effect will decrease by the increasing temperature of sintering temperature.

More infomation about tungsten copper electrode infiltration, click here:

http://news.chinatungsten.com/en/tungsten-information/79730-ti-10171

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Gas Sensing Response Principle of WO3

Rair and Rgas are the resistance of sensor in dry air and target gases, respectively. Usually, in oxidizing atmosphere, the oxide surface is covered cermet turning inserts by negatively charged oxygen adsorbate and the adjacent space charge region is electron-depleted: the oxide layer presents therefore a high resistance (Rgas＞Rair). Under reducing conditions, the oxygen adsorbate is removed by the reaction with reducing gas species and the electrons are re-injected into the space charge layers: as a result, the oxide layer resistance decreases (Rgas＜Rair).  Besides, the voltage change of oxide may be used to illuminate the gas sensitivity at times. Therefore, the change of resistance, conductivity or voltage could be used as the parameters to scale the sensitivity.

Nano AlN Effect on W-Cu Composite Material Density and Hardness

By experiment, carbide cutting tools we can find that with the increasing AlN, W-Cu composite density tends to decrease. Theoretical density reduction is due to the low density of AlN itself (3.26g / cm3), which is much less than that of tungsten and copper. So with the increase of AlN content, the theoretical density of the whole material decreases naturally. While the measured density decrease is not only because of the low density of AlN itself, it also includes from relative density: one is the addition of nano AlN particles hinders the rearrangement of tungsten particles, which the tungsten copper material densification in liquid sintering depends on. The higher the content of nano-AlN particles, the more obvious the blocking effect, the more difficult the rearrangement of tungsten particles, the more difficult to fill the pores; the other is the wetting ratio of AlN particle is not as good as W and Cu at high temperature, so the addition will decrease the density of tungsten copper composite materials. In a word, few nano AlN particles have no effect on W-Cu composite material and it can further improve physical and mechanical properties.

Proportion	Theoretical Density(g/cm3)	Measured Density(g/cm3)	Relative Density(g/cm3)
W30Cu	14.34	14.22	98.94
W30Cu/0.25AlN	14.22	14.06	98.87
W30Cu/0.5AlN	14.10	13.87	98.37
W30Cu/1AlN	13.87	13.59	97.98
W30Cu/2AlN	13.42	12.54	93.44

W-Cu composite material usually uses Brinell hardness (HB) or Rockwell hardness (HR). In accordance with the addition of AlN and hardness measurements plotting the change curve, we can clearly found that the hardness of W-Cu composite material is improved with the increasing amount of nano AlN particles, which also indicates the addition of AlN particles reduced the interfacial bonding, but it played the role of fine grain strengthening and dispersion strengthening, especially for matrix copper. However, when the content exceeds 1%, the increasing trend of hardness is slowed down, because the density of tungsten-copper composite decreases, which leads to the increase of porosity in matrix.