The through hole is one of the important components of PCB. Its function is to fix or locate the electrical connection channels and devices between layers. Mechanical drilling with PCB micro-drill is the most commonly used processing method.

In the future, the refractory tungsten metal and structural material steel need to be joined together in the divertor part of fusion equipment. Due to the huge difference of thermal expansion coefficient between tungsten and steel, the joint of tungsten and steel obtained by conventional welding method has large residual stress and working pressure, which will lead to deformation and cracking.

Transition metal chalcogenides, as a new two-dimensional layered material, have similar properties to graphene and are widely used in field-effect transistors, sensors, energy storage and catalysis. Tungsten selenide, as an undeveloped transition metal chalcogenide, is a promising non-noble metal catalyst. Its performance is also influenced by the phase and electronic structure.

The balancing shaft of aircraft engine is a simple and practical engine part. It can effectively reduce the vibration of aircraft in flight, because when the engine is in working state, the piston moves very fast and the speed is very uneven. The balancing shaft can effectively improve the comfort of passengers. Tungsten-based high specific gravity alloys are commonly used in balancing axles of aircraft engines.