HYPERVELOCITY OXYGEN FUEL (HVOF)

Process
High Velocity Oxygen Fuel or HVOF is the most recently developed of the thermal spray processes in use at CTS. Combustible gas and oxygen are used to produce a flame that is directed at very high velocity through a gun by use of a converging, diverging nozzle arrangement. Powder is injected into the hot gas stream and softened, then impacted with very high kinetic energy onto the workpiece layer by layer until the desired thickness is built up. The resultant coatings approach theoretical density and exhibit outstanding performance characteristics.

Characteristics
HVOF coatings are the densest among the processes and also the most securely bonded. Bond strength usually exceeds the strength of the glue used in the tensile bond test - normally above 10,000 psi. Coating porosity for many materials are 1% or less. These are the most wear resistant and corrosion resistant coatings of all the processes.

Materials
Coatings of tungsten carbide materials are optimized using HVOF because the HVOF flame is not hot enough to cause the formation of complex phases of carbides. Tungsten carbide coatings produced with the HVOF process are among the most wear resistant coatings possible with thermal spray technology. These coatings routinely outwear chrome plating by factors in excess of five to one.

Coatings of high alloys are another popular use for HVOF - oxidation resistant, heat resistant alloys such as hastelloys, inconels, stellites, tribaloys and some proprietary alloys make up a key area of HVOF coatings. All of these materials protect against temperature, wear, chemical attack or some combination. HVOF is also used frequently as a component rebuilding process utilizing steel and stainless steel as coating materials.