Currently, the tungsten electrode, rare earth tungsten electrode and the composite electrodes are widely used in chemical, electrical, mechanical, construction, aerospace and other fields. But with the development of scientific and technological, tungsten inert gas welding and plasma welding field, there are higher requirements of electrode material and performance have been put forward . The properties of lanthanum tungsten electrodes are superior to thorium tungsten electrode and cerium tungsten electrode which is one of the most widely used electrodes.

Lanthanum tungsten electrodes have good mechanical cutting performance, creep resistance, ductility and high recrystallization temperature is currently the most popular electrode. It was developed from the European country in the 1980’s to replace thorium tungsten electrode. The tip colors of lanthanum tungsten electrodes are varies which depend on the amount of lanthanum oxide (La2O3) doping. When La2O3 doping amount is 0.80 to 1.20%, the tip color is black; when La2O3 doping amount is 1.30 to 1.70%, the tip color is golden yellow; when La2O3 doping amount is 1.80 to 2.20%, the tip color is sky blue.

Lanthanum tungsten electrode is mainly used in DC welding and AC welding. The experiment found that the 1.5% lanthanum oxide content in lanthanum tungsten electrode has similar conductive properties with thorium tungsten electrode which has 2% thorium oxide content. Besides, the burn rate of lanthanum tungsten electrode is smaller and has longer service life. On the other hand, lanthanum tungsten electrode is a non-polluting, non-radioactive green electrode. So it concern in European countries and Japan is very high.

Lanthanum tungsten electrode production method:

1. Add the appropriate amount of La2O3 powder into tungsten trioxide powder, after twice reduction to give W-La2O3 powder. The first reduction temperature is at 600 ~ 700 ℃and time is about 2 to 3 hours; the second reduction temperature is controlled at 800 ~ 970 ℃ and the hydrogen flow is 0.5-2.0m3 / h.

2. After pressing, swaging, stretching, straightening, polishing and other processes obtains the desired electrode rod.

With argon arc welding, plasma welding, cutting, spraying technology continues to update and development, the requirement of electrode materials are increasingly high. In 1972, China first time success developed cerium tungsten electrode, which has a non-radioactive, low-melting, high thermal electron emission ability, arc stability, heat concentration, long life, easy to maintain the shape of the tip and other good properties. What’s more, it can replace thorium tungsten electrodes which has radioactivity.

Cerium tungsten electrode is kind of rare earth tungsten electrodes which added 2% cerium oxide (CeO) into tungsten matrix electrode product production by powder metallurgy, rolling, grinding and polishing and other processes. It is mainly used in low current DC welding, because it has a good arc and welding properties. On the other hand, cerium tungsten usually uses in welded pipes, stainless steel products and small parts welding. Cerium tungsten electrode is not suitable for use in high current conditions, because at high currents cerium oxide will quickly move to the high heat zones, namely the tip of electrode welding, causing cerium oxide uniformity damage. Uniformity of cerium oxide is an important influence factor affecting properties of cerium tungsten electrode, therefore cerium tungsten electrodes is not suitable for high current conditions.

Cerium tungsten electrode material properties are as follows: the work function: 2% Ce-W2.4ev; α-ray dose: 2% Ce-W2.42 × 10-5 curie / kg; oxidation resistance: high oxidation resistance.

Cerium tungsten electrode arc performance: the cathode voltage drop: 2% Ce-W12.0V; cathode spot: the cathode spot and service life are closely linked and it has small cathode spot and loss; electrode emission current density: higher; minimum arc voltage: 12V.

Cerium tungsten electrodes application performance: the burning rate: low; reliability of repeatedly arc and loss rate: arc stability, low loss rate; weld penetration: good.

The first part mainly describes the concept and the function of transition layer, this part we introduce some experiments about it. Related researchers certain related technology by using titanium (Ti) and nitrogen (N) ion and the substrate to produce a large number gradually decreased reaction TiCN N ions, so that transition layer containing C, N decrement amount to the surface direction, until the final surface titanium This is to the surface at the time of planting, diamond crystals partially reacted with a titanium Ti titanium carbide TiC, as part of the process of diamond film deposition seed, in order to improve the bonding strength between the diamond film and the buffer layer and the diamond nucleation density; some studies have found that uses TiN and TiCN deposition as the transition layer, it will make diamond film with high purity, but the speed of nucleation is slow. Therefore, they attempt to directly deposited on the surface layer of aluminum carbide substrate, or discontinuous deposit a certain amount of diamond grains, thereby improving the imbalance in thermal expansion coefficient between the TiN / TiC and diamond, making the diamond and speed and adhesion have been significantly improved.

Relevant foreign scholars have used plasma pulsed laser melting method in cemented carbide substrate surface layer of boron nitride (BN) film, which not only eliminates the adverse effects of cobalt Co brought, and significantly improve the binding force between diamond coating layer and tungsten carbide matrix. In addition, Chinese scholars are based on chromium carbide buffer layer deposition CVD diamond coating, and spectral analysis by SEM showed that the deposition process have a more significant impact on the diamond's shape and composition, and ultimately to the complete crystalline, less non-diamond ingredients with carbide substrate binding tightly CVD diamond coating.