What characteristics should thermal spray powder materials have?

       Thermal spray powders are divided into self-fluxing alloys, self-bonding alloys, corrosion-resistant and oxidation-resistant alloys, ceramics, cermets and composite powders. Each powder must take into account the effects of its particle size composition, particle shape, flowability and composition. The shape, particle size and particle size distribution, bulk density, fluidity and surface quality of thermal spray powder are the basic characteristics of the powder, which are an important part of the performance of ceramic materials for thermal spray.General thermal spray powder materials should have the following characteristics:

(1) The particle morphology of thermal spraying powder mainly refers to the geometric shape and surface characteristics of the powder particles. Since the degree of powder spheroidization is not only related to the atomization powder milling method and atomization milling process parameters, but also to the chemical composition of the powder itself. Therefore, the spheroidization degree of different types of powders is also different, but it should be ensured that the spraying process can be Smooth and even powder feeding. There are sometimes holes of different sizes in the metal powder particles for thermal spraying formulated by the atomization method. Some holes penetrate to the surface, and some holes are closed inside the particles. If the spraying process is improper, it will have a direct impact on the quality of the coating.

(2) The particle size of the powder. The selection of powder particle size and its range is mainly determined by the spraying process method and spraying process specification parameters. Even if the powder particle size range is the same, the proportion of its particle size grade composition is not necessarily the same. Quality, powder bulk density and fluidity have a direct impact.

(3) Powder bulk density. Powder bulk density refers to the mass per unit volume of powder when it is loosely packed. Since the powder bulk density is related to the spheroidization degree of the powder, the size and quantity of the pores inside the powder particles, the powder particle size composition and other parameters, it also affects the quality of the spray coating.

(4) The fluidity of thermal spray powder The fluidity of powder is the time required for a specified amount of powder to freely flow through a standard funnel with a specified aperture, which is usually characterized by the time required for 50g powder to flow through a standard funnel with a 2.5mm aperture. It has a certain influence on the spraying process and spraying efficiency.

The hoses and air lines of thermal spray equipment should be inspected regularly, and equipment found to be defective should be repaired or replaced immediately. When the thermal spraying equipment is finished spraying, or when the equipment is shut down and left unattended, all the gas in the regulator and hose should be released, and operate in the following order: (1) Close the gun valve. (2) Close the air valve. (3) Open the gun valve. (4) Turn the adjusting screw to the free state. (5) Close the gun valve. (6) Close the tank valve or the branch valve in front of the regulator. 

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