Ceramic Coatings for Wear Resistance: An Overview of Common Types Used in Thermal Spraying

Alumina

Alumina is a frequent solution for several coating challenges. It is harder than many other ceramic coatings, is an excellent electrical insulator, and the nearly pure white coating can be polished to a good finish. It is often used when electrical isolation is required and where high abrasion resistance is needed.It is also frequently preferred when the coated surface will be visible because of its clean white color. 

Coatings of alumina are especially useful in corona treating applications, due to their uniform insulation properties and high wear resistance.

Chrome Oxide

Chrome oxide is a popular ceramic coating due to its high level of wear resistance and low coefficient of friction. It is applied where high-speed rotation is required, such as on bearing surfaces and lip seals, where it can help to reduce friction and minimize wear.

Along with it's wear-resistant properties, chrome oxide is also resistant to oxidation and chemical attack, making it an excellent choice for rotary seal applications in fluid handling equipment. Chrome oxide is comparable to alumina in hardness, but is typically capable of being ground to finer finishes than coatings of alumina.

Titanium Dioxide

Titanium dioxide shares many physical similarities with alumina and chrome oxide, though it is slightly less hard than both of these and is typically easier to grind and polish. Like the other ceramics, it is non-corroding and electrically insulating. Due to its lower hardness, it is often preferred in applications where continuous motion or high-speed contact is less likely.

The ability to grind titanium dioxide to fine finishes makes this coating an ideal mating surface for valve components. Moving and stationary items like balls and seats can both be coated with titanium dioxide and lapped to a precision fit and finish. The two mating surfaces can move freely against one another without galling because there is no metallic material and no opportunity for adhesive wear.

Zirconia

Zirconia is an off-white ceramic with a substantially higher melting point than most other ceramic materials. It is hard and brittle, but its extraordinarily high melting point makes it ideal for thermal insulating applications. For this use, coatings are often applied with an intentionally porous or open structure to minimize the available pathway for heat transfer from the surface of the coating to the substrate. Since the operating environment for these applications is typically open, with only air or hot gas in contact with the coated surface, the lower wear resistance of zirconia coatings is typically not a concern. 

Coatings of yttria stabilized zirconia or magnesia zirconia are ideal thermal barrier coatings in the combustion and hot gas path components of turbine engines, where their thermal insulating properties protect metal components from the extreme temperatures of combustion and permit the turbine to be run hotter and at higher power than would be possible without this protection. 

These are just a few of the many types of ceramic coatings used in thermal spraying for wear resistance. Each type offers its own unique benefits and can be tailored to fit specific requirements. When selecting the right coating for your application, it's important to consider all of the factors such as temperature, abrasion resistance, corrosion resistance, and electrical insulation. With the right combination of these properties, you can ensure that your components remain in top condition even in the most extreme conditions.

About Hayden Corp.

Hayden Corp. offers a wide range of ceramic coatings for wear resistance and other applications. Our experienced team can help guide you in selecting the coating that is best suited to your application, so you get the highest performance out of your component parts. Contact us today (413) 734-4981 for more information or request a quote online.