Thermal spraying techniques are coating processes in which melted (or heated) materials are sprayed onto a surface. The "feedstock" (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame)
During the 1980s, a class of thermal spray processes called high velocity oxy-fuel spraying was developed. A mixture of gaseous or liquid fuel and oxygen is fed into acombustion chamber, where they are ignited and combusted continuously. The resultant hot gas at a pressure close to 1 MPa emanates through a converging-diverging nozzle and travels through a straight section. The fuels can be gases (hydrogen, methane, propane, propylene, acetylene, natural gas, etc.) or liquids (kerosene, etc.). The jet velocity at the exit of the barrel (>1000 m/s) exceeds the speed of sound.
Wire arc spray is a form of thermal spraying where two consumable metal wires are fed independently into the spray gun. These wires are then charged and an arc is generated between them. The heat from this arc melts the incoming wire, which is then entrained in an air jet from the gun. This entrained molten feedstock is then deposited onto a substrate. This process is commonly used for metallic, heavy coatings.
Flame spray, also known as oxy/acetylene combustion spray is the original thermal spray technique developed about 100 years ago. It uses the basic principles of a welding torch with the addition of a high velocity air stream to propel molten particles onto the substrate. The coating material can be either a wire or powder form. Often flame spray coatings are fused after being applied to enhance bond strengths and coating density.
Applying thermal sprayed ceramics onto metallic substrates offers enhanced surface properties. Examples include thermal or electrical insulation, and wear and corrosion resistance. We can tailor a complete coating system for your specific needs with our flexible and expert resources.
In this process, a combustion powder spray gun is utilized to deposit a wide variety of materials onto a substrate. The powders used for spray and fuse hardfacing are typically compositions of Ni, Cr, Co, Bo, Fe, W and WC in varying blends. After the coating has been sprayed to a pre-determined thickness, an oxygen-acetylene torch, or a furnace, is used to heat the part to approximately 2000 degrees Fahrenheit, fusing the coating within itself and to the substrate, thereby achieving a true metallurgical bond. With this process, coatings can be applied with a hardness up to 80Rc.
Stellite alloy is a range of cobalt-chromium alloys designed for wear resistance. It may also contain tungsten or molybdenum and a small but important amount of carbon. It is a trademarked name of the Kennametal Stellite Company and was invented by Elwood Haynes in the early 1900s as a substitute for cutlery that stained (or that had to be constantly cleaned).