Selection of thermal spray materials

Selection principle

Different usage requirements of materials surface and different spray process make the types of thermal spray materials different. The following principles should be followed primarily when selecting thermal spray materials.

1 Select the material that best suits the functional requirements according to the working environment of the workpiece to be sprayed, usage requirements and the known properties of various spray materials.

2 Try to make the thermal expansion coefficient of the spray material and the workpiece material close to each other to obtain a high-quality spray coating with high bond strength.

3 The selected thermal spray materials should be compatible with the spraying process and equipment.

4 spraying materials should have low cost with wide source.

(1) Select according to thermal spraying process

When using thermal spray materials, they should be selected by different spray processes and methods according to properties of different spray materials. The spraying methods for bonding the underlying spray material are shown in the figure below.

Spray materials

Flame powder coating

Plasma arc powder coating

Wire arc spraying

Wire flame spraying

Ni-Al(80%/20%)

 

Ni-Al(95%/5%)

Ni-Cr(80%/20%)

 

 

CuAl10


(2) Select according to the requirements of the workpiece to be sprayed.

In the case where the surface of the workpiece to be sprayed is required to be worn during spraying, the commonly used materials are self-fluxing alloy materials (nickel-based, cobalt-based and iron-based alloys) and ceramic materials, or a mixture of both. Spray materials such as a mixture of a carbide and a nickel-based self-fluxing alloy is suitable for a case where high temperature resistance is not required and only wear resistance is required. Usually the working temperature of the carbide spray layer should be below 480C, when exceeds this temperature, it is best to use titanium carbide, chromium carbide or ceramic materials. Spray coatings formed of high carbon steel, martensitic stainless steel, molybdenum or nickel chrome alloy and other spray materials are particularly suitable for sliding wear.


Zinc, aluminum, austenitic stainless steel, aluminum bronze, cobalt-based and nickel-based alloys are often used under conditions where the workpiece to be sprayed is resistant to atmospheric corrosion, of which the most widely used are zinc and aluminum. The corrosion-resistant spray material itself has good corrosion resistance, but if the sprayed layer is not dense and has pores, the corrosive medium will penetrate. Therefore, the density and thickness should be ensured during spraying, and the sprayed layer should be sealed.

In order to form good bonding between the sprayed workpiece and the sprayed layer, sometimes it is possible to bond the underlying spray material to create a transition between the workpiece and the sprayed layer. Molybdenum, nickel-chromium composite materials and nickel-aluminum composite materials can be used as the coating material for the bonding underlayer. However, when selecting the underlying coating material, the corrosiveness and temperature of the environment should be two major considered issues.