Scope of application of thermal spray technology

       Whether it is a mechanical part or a metal part, the prominent problem is surface wear or corrosion, or both. The following is a brief description of the coating application guidelines:



1. Wear-resisting - the application field of high temperature and low temperature thermal spraying technology. These coatings can be divided into the following categories:



(1) Resistance to Adhesive Wear or Scratch - Adhesive wear or scratches occur when two surfaces slide against each other and debris slides from one surface to the other. Typical coatings are cobalt based tungsten carbide, nickel chromium/chromium carbide coatings.



(2) Abrasive wear - abrasive wear occurs on softer surfaces with wear between the two surfaces. Abrasive wear also occurs when fibers and filaments pass through surfaces at high speeds. Proprietary typical coatings are cobalt-based nickel-chromium alloys, self-fluxing alloys mixed with molybdenum, and chromium oxide coatings.



(3) Anti-micro-vibration wear - repeated loading and unloading can cause periodic stress, resulting in surface cracking and large-area shedding. Typical coatings are alumina/titania coatings.



(4) Anti-cavitation - mechanical impact of liquid flow on the surface. A typical coating is an aluminum bronze coating.



(5) Erosive wear resistance - erosion wear that occurs when gas or liquid carries particles at high speed and hits the surface. Typical coatings are alumina/titania and alumina coatings.







2. High temperature and oxidation resistance - This coating has the ability to resist chemical or physical decomposition to improve the high temperature performance of the part. These coatings fall into the following categories:



(1) Thermal barrier coating - acts as a thermal barrier between the component and the high temperature environment. A typical coating is a zirconia coating, which is stabilized by yttrium oxide.



(2) High temperature oxidation resistant coating - high temperature oxidation resistant substrate. Typical coatings are Ni/Cr coatings.



(3) High temperature corrosion resistant coating - protects the substrate exposed to hot corrosive gas. Typical coatings are Ni/Cr coatings.







3. Anti-corrosion coating - The choice of this coating is complicated because the parts are in use, the ambient temperature and various media have some requirements on the coating material. Cobalt-based alloys, nickel-based alloys and oxide ceramics are usually used as coating materials to prevent the penetration of corrosive media by improving the compactness of the coating. Reasonable selection of coating materials and oxidation/reduction potentials of parts substrates to prevent electrochemical corrosion, and coating of sealants to inhibit corrosion.







4. Conductive or insulating paints - These paints fall into the following categories:



(1) Conductive coating - a typical coating is copper coating.



(2) Insulating paint - a typical coating is an alumina coating.



(3) Shielding coating - A typical electromagnetic interference (EMI) or high frequency interference (RFI) coating is a copper coating.







5. Recycled coatings - These coatings are mainly used to repair worn or poorly machined parts. The choice of coating material mainly depends on the use requirements of the part.