Plasma welding technology, as an advanced surface modification process, has been widely used in various industrial fields in recent years. The technology utilizes a high-temperature plasma arc to melt the welding material and deposit it on the surface of the substrate, thereby forming a coating with excellent properties. Although plasma welding technology has many advantages, but in the actual operation of the process still need to pay attention to the following key matters, in order to ensure the success of the process and the stability of the coating quality.

1. Material selection
Substrate selection
The selection of substrate material is crucial to the effect of plasma welding. The chemical composition, physical properties and heat treatment status of the substrate will affect the bonding strength and performance of the welding layer. Therefore, before welding, the substrate should be fully analyzed and pre-treated to ensure that its surface is clean and free of oxides and other impurities.

Selection of welding material
The selection of the welding material is also critical. Typically, welding materials need to have good resistance to wear, corrosion and high temperatures. Common welding materials include nickel-based alloys, cobalt-based alloys and tungsten carbide. When selecting welding materials, comprehensive consideration should be made according to the actual application requirements and working environment.

2. Process parameter setting
Plasma arc current and voltage
The current and voltage of plasma arc directly affect the quality and thickness of the welding layer. Too high current and voltage may lead to overheating of the base material, affecting its mechanical properties; while too low current and voltage may lead to insufficient melting of the welding material and the formation of an uneven coating. Therefore, the current and voltage of the plasma arc should be set reasonably according to the specific melting material and substrate.

Traveling speed of spray gun
The moving speed of the spray gun has an important influence on the uniformity and thickness of the molten coating. Too fast moving speed may lead to too thin and uneven welding layer; while too slow moving speed may lead to too thick welding layer, or even the phenomenon of molten droplet flow. Usually, the moving speed of the spray gun should be reasonably adjusted according to the melting point of the welding material and the thermal conductivity of the base material.

3. Environmental control
Gas protection
In the process of plasma welding, the use of protective gases (such as argon, helium, etc.) can effectively prevent the oxidation of the welding material at high temperatures, thus ensuring the quality of the coating. According to the nature of the coated material and process requirements, select the appropriate protective gas and control its flow and purity.

Operating environment
Plasma welding is usually carried out in a high temperature, high brightness environment, so the operator should wear appropriate protective equipment, such as protective glasses, protective gloves and protective clothing. In addition, the operating environment should be well ventilated to prevent the accumulation of harmful gases.

4. Follow-up treatment
Cooling treatment
After the welding is completed, the substrate and the welding layer need to undergo appropriate cooling treatment. Too fast a cooling rate may cause cracks or internal stresses in the coating, while too slow a cooling rate may affect the densification and bonding strength of the coating. Typically, natural or controlled cooling can be used to ensure the quality and performance of the coating.

Inspection and Evaluation
After welding, the coating should be subjected to rigorous testing and evaluation, including the thickness, hardness, bond strength and wear resistance of the coating. By means of non-destructive testing and metallographic analysis, potential problems can be found in time and repaired and improved accordingly.

Summarize
Plasma welding technology, as an efficient and reliable surface modification method, has a wide range of application prospects. However, its advantages can only be fully utilized to obtain high-quality fusion welding layer if the operating procedures are strictly observed, the materials are reasonably selected and the process parameters are controlled. It is hoped that the detailed introduction of this paper can provide useful reference for relevant practitioners and promote the further development and application of plasma welding technology.