Whether it is a mechanical part or a metal part, the most prominent problem is surface wear or corrosion or both. Here is a brief introduction to the application guide for thermal spray coating:
The wear-resistant coatings produced by thermal spray technology have a wide range of applications at high temperatures and low temperatures. These types of coatings are specifically divided into the following categories:
(1) Adhesive wear or scratching – the two surfaces slide relatively, and the debris sticks from one surface to the other, which is prone to adhesive wear or scratches. Typical coatings are cobalt-based tungsten carbide, nickel-chromium/chromium carbide coatings.
(2) Wear-resistant grain wear – abrasive wear occurs when a hard surface slides on a soft surface and there is wear between the two surfaces. Abrasive wear also occurs when the fibers and threads pass at high speed on the surface. The typical coatings are cobalt-based nickel-chromium alloys, self-fluxing alloys mixed with molybdenum and chromium oxide coatings.
(3) Resistance to fretting wear – repeated loading and unloading produces cyclic stresses that cause surface cracking and large area shedding. A typical coating for the application is an alumina/titania coating.
(4) Cavitation wear resistance – liquid flow produces mechanical shock on the surface. A typical coating for the exterior is an aluminum bronze coating.
(5) Erosion-resistant wear–Erosion wear occurs when a gas or liquid carries particles at high speed to impact the surface. A typical coating for the application is an alumina/titania or alumina coating.
High-temperature resistant oxidation resistant coating
These coatings can resist chemical or physical decomposition, improve the high-temperature performance of the parts. These types of coatings are divided into the following categories:
(1) Thermal barrier coating – acts as a thermal barrier between the part and the high-temperature environment. A typical coating is a zirconia coating that is stabilized with yttria.
(2) High-temperature resistant oxidation coating – protects the substrate against high-temperature oxidation. A typical coating is a nickel/chromium coating.
(3) Heat-resistant corrosion coating – protects the substrate exposed to hot corrosive gases. A typical coating is a nickel/chromium coating.
This type of coating is more complicated, because it has certain requirements on the ambient temperature and various media on the coating material. Cobalt-based alloys, nickel-based alloys, and oxide ceramics are generally used as coating materials to block the penetration of corrosive media by increasing the compactness of the coating.
Conductive coating or insulating coating
These coatings are divided into the following:
(1) Conductive coating – The typical coating is a copper coating.
(2) Insulating coating – The typical coating for the application is an alumina coating.
(3) Shielding coating – A typical coating for electromagnetic interference (EMI) or high-frequency interference (RFI) is a copper coating.
Restore size coating
This type of coating is primarily used to repair parts that are worn or out of machining. The choice of coating material depends primarily on the requirements of the part.
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