HVOF SPRAY The HVOF (High Velocity Oxy-Fuel) Thermal Spray Process is basically the same as the combustion powder spray process (LVOF) except that this process has been developed to produce extremely high spray velocity.

Fuel (kerosene, acetylene, propylene and hydrogen) and oxygen are fed into the chamber. Combustion produces a hot high pressure flame which is forced down a nozzle increasing its velocity. Powder is preferably fed axially into the combustion chamber under high pressure or fed through the side of nozzle where the pressure is lower.   Due to higher velocity the bond-strength of the coatings are higher. The powder to be sprayed are often not melted but accelerated in a high temperature and high velocity gas stream causing the phase of the sprayed material to change from solid to plastic (semi-molten) form. When these particles strike the prepared substrate, they solidy to form a very dense and low porosity coating. HVOF is best recommended for Carbide matrix coatings. Carbide coatings sprayed by HVOF renders good hardness, wear resistance and abrasion resistance characeteristics. HVOF Sprayed Carbide coatings have a perfect alternative for Hard Chrome platings.      Widely used Carbide Coatings Sprayed by HVOF Process: Tungsten Carbide: Excellent Wear and Abrasion Resistance Chrome Carbide: Excellent Corrosion Resistance Carbide powder are available in many variants for meeting requirements of specific applications. Good quality Metal & Alloy coatings can also be achieved using HVOF.

Characteristics of HVOF Coatings:  Material Form  Powder  Heat Source  Accelerated Oxy-fuel flame  Flame Temperature (°C)  > 3000  Gas Velocity (m/sec)  700 to 1200  Porosity (%)  < 1  Coating Adhesion (MPa)  > 70 Advantages:   Coatings are dense with very low porosity Excellent, tenaciously bonded coatings Low oxide metallic coatings Optimized microhardness Disadvantages: Process should preferably be automated Very high noise emissions