Thermal Spray Material Selection Guide

       

Proper selection of coating materials is critical to ensuring the desired coating properties. When choosing the coating material, the working conditions of the workpiece and the properties that the coating needs to have should be considered first, as well as the material, batch, economy of the workpiece and the thermal spraying method to be used. According to the function of the coating, the coating can be roughly divided into corrosion-resistant coating, wear-resistant coating, anti-friction and sealing coating, high temperature resistant thermal barrier coating, insulating or conductive coating, dimensional repair coating, etc.

The reason for the failure of the surface-coated workpiece in the throwing process is often not caused by a single factor, so there is not necessarily a simple relationship between meeting the requirements of the working conditions and the coating performance. The working conditions should be analyzed in detail, and the coating structure, physical, chemical, mechanical and other properties should be comprehensively considered according to the references or experimental data, so as to determine one or several coating materials.

Wear-resistant coatings are one of the main areas of application for surface coating technology. Although there is a rough relationship between coating hardness and wear resistance, hardness does not fully represent the wear resistance of surface coatings. Because different wear types have different requirements for material properties, and wear is often accompanied by impact, corrosion, fatigue and temperature effects.

The selection of surface coating materials cannot blindly pursue high-performance or high-priced coating materials, resulting in unnecessary waste, and the price of materials cannot be used as a standard for selecting coating materials. Under the premise, it is particularly important to use inexpensive coating materials as much as possible in mass production. For example, a nickel-based alloy coating material can be used without a drill-based alloy coating material.

When selecting a surface coating material, generally follow the steps below:

Analyze working conditions and parts performance to understand failure causes and requirements for coating performance;

List available coating materials;

Analyze the compatibility of the candidate material with the base material and the thermal spraying method that can be used;

Carry out laboratory or field tests when necessary;

Determining coating materials taking into account service life, cost and factory conditions;

Determine surface coating method and develop coating process.

The following is a brief introduction to the properties of the coatings commonly used at present to provide a reference for the correct selection of the spraying process.

Generally speaking, the main purposes of using thermal spray coating are as follows: (1) anti-corrosion coating; (2) anti-wear coating; (3) anti-friction and sealing coating; (4) high temperature and heat resistance Barrier coatings; (5) insulating or conductive coatings; (6) dimensional repair coatings, etc. Different coatings should be used for different purposes.

Corrosion resistant coating

The selection of corrosion-resistant coating materials is more complicated. The working state, working temperature, working environment and various corrosive media of the parts all increase the requirements for coating materials. Corrosive environments may be aqueous, gaseous, or various chemical media, and may have a wide temperature range. In the presence of gas, the burning gas or unburned fuel may also react with other substances at the appropriate temperature, forming a very complex corrosive environment. There are basically three mechanisms for anti-corrosion: