Industrial coatings comprise epoxy, phenolic, silicone, and urethane, but increasing demands for performance have ushered in new materials and process advancements in the industrial coatings marketplace.
Surfaces subject to abrasive or erosive wear, extreme heat, corrosion, or require dimensional restoration or electrical insulation, as examples, can benefit greatly from high velocity oxygen fuel (HVOF) type coatings. Developed in the 1980’s, this branch of thermal spray coatings brings surface property enhancements that can include: adhesive strength, hardness, and resistance to abrasion or permeation, using a wide range of alloyed metals and ceramic powders transformed into a plasticized state while fed through a high temperature gas stream.
Also referred to as “wire flame spray” or the “combustion wire coating process”, the process utilizes an oxygen-fuel gas flame for the heat source. Both wire form and solid rod feed-stock are utilized.
The outermost tip of the wire or rod is melted as it passes through the flame and is “atomized” into very small particles by a surrounding jet of compressed air, propelled to the work-piece to form the coating at the surface.
Substrate temperatures remain comparatively low in the HVOF coating process, little heat is imparted to the work-piece, so risk of distortion from heat is minimal, no more than a few hundred degrees F, typically, making most metals compatible with the coating process, including: iron, steel, austenite or martensite grades of stainless steel, alloys of copper and aluminum. Builds (coating thickness) as high as 0.250 inch are attainable.
Additionally, the RoHS compliance of HVOF coatings brings significant advantage over metal finishing processes such as hard chrome plating.
Markets for high velocity oxygen fuel (HVOF) industrial coatings include: automotive, medical, defense and aerospace, printing and paper, food processing, industrial and manufacturing, military, aerospace and defense, and more.
Restoring surface dimensions of worn components is a common use of this coating process. However, uses involving line or point contact, shear loads, higher stress, should be avoided, such as gear teeth, splines or threads.
For newly-engineered surfaces requiring performance solutions to abrasive wear, HVOF coatings based on tungsten carbide can be an excellent choice. In applications of surface fatigue, motion between contacting areas, overcoming friction relating to wear, molybdenum can serve well.
Thermal spray coatings can solve a variety of issues relating mechanical, electrical, or corrosion. However, keep in mind that no strength is added to the base material. Surfaces must be able to withstand the mechanical loads in service; nitride or heat treat as needed.
HVOF is a versatile coating process, offers a range of materials as metal finishes. Extrusion dies, piston rings, bearing journals are common examples of use. What surface properties will you bring to your product or process, using high velocity oxygen-fuel coatings?