What are the differences between supersonic spraying and plasma spraying?

Supersonic spraying and plasma spraying are both high-energy spraying technologies widely used in material coating, surface repair, and anti-corrosion fields. Although both spraying techniques can achieve high-quality coatings, their working principles, spraying effects, and applicability are different. This article will analyze the differences between supersonic spraying and plasma spraying from multiple perspectives.

1. Working principle

Supersonic spraying refers to the process of cutting the sprayed material with supersonic airflow during high-speed spraying, generating a high-temperature and high-pressure material flow, heating and accelerating the material powder to a predetermined speed, and forming a bonded coating on the surface of the substrate. Supersonic spraying generally adopts collimated spraying, which means that the powder is vertically ejected from the nozzle, so that the powder flow trajectory is perpendicular to the substrate surface. During supersonic spraying, the airflow velocity can reach 700-1000m/s or even higher, and the contact time between the coating and the substrate is very short. Therefore, the coating structure is dense, the hardness is high, and it has good adhesion and wear resistance.

Plasma spraying, also known as plasma gas spraying, refers to the process of melting powder materials through plasma spark heating and forming coatings under the support of high-speed plasma airflow. In plasma spraying, the plasma gas generated by heating the powder can accelerate the material to a high speed, usually 1000-2000m/s, and melt into a coating on the surface of the substrate. The nozzle of plasma spraying is usually angle spraying, which means that the powder is sprayed from the nozzle at a certain angle to form a coating under the interaction with the substrate surface. Plasma spraying technology has the advantages of simple operation, fast spraying speed, high forming efficiency, and can also prepare coatings with high roughness and thickness.

2. Spray effect

The spraying effects of supersonic spraying and plasma spraying are slightly different. The coating density of supersonic spraying is high, the hardness is high, the melting point and corrosion resistance are good, and its advantages mainly lie in the density and uniformity of the coating. The thickness of the supersonic spray coating is moderate, usually between 20 microns and 200 microns, which can effectively protect the surface of the substrate. However, when the heat input is large, materials sprayed at supersonic speeds are prone to sintering, which affects the quality of the coating.

The advantages of plasma spraying are fast spraying speed, easy control of coating thickness, and the ability to prepare uniform coatings. Due to the extremely high heating temperature of plasma airflow, most materials can be heated to their melting point, thereby achieving rapid coating forming. In plasma spraying, the control of coating thickness is relatively easy, which can be achieved by adjusting the material spraying speed and airflow pressure. Plasma spraying also has the ability to prepare high-temperature alloy coatings.

3. Scope of application

Both supersonic spraying and plasma spraying can spray various materials, such as metals, ceramics, glass, plastics, etc. However, the types and fields of materials they are applicable to are slightly different.

Supersonic spraying is commonly used to prepare coatings of high heat resistance and high hardness materials such as metals, alloys, and ceramics. Due to its thickness control capability, supersonic spraying can also be used for surface modification and protection in fields such as medical equipment, automotive components, aerospace, and energy.

Plasma spraying has a wide range of applications, not only for coating materials such as metals, ceramics, and glass, but also for coating high-temperature materials such as oxides and intermetallic compounds. Plasma spray coating can form biomaterials, hard alloys, ceramic coatings, etc. on the surface, and can also be applied in fields such as molds, building materials, power electronics, biomedicine, petrochemicals, etc.

In summary, although supersonic spraying and plasma spraying belong to high-energy spraying technologies, they differ in their working principles, spraying effects, and applicability. Supersonic spraying is known for its dense and uniform coatings, making it suitable for applications that require high hardness, corrosion resistance, and thermal barrier properties. Plasma spraying has a wide range of applications and can be used to prepare high-quality coatings, high-temperature alloy coatings, etc. It also provides more choices for the industrial field.