High Velocity Oxygen Fuel Spraying (HVOF)
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 a combustion 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. A powder feed stock is injected into the gas stream, which accelerates the powder up to 800 m/s. The stream of hot gas and powder is directed towards the surface to be coated. The powder partially melts in the stream, and deposits upon the substrate. The resulting coating has low porosity and high bond strength.
HVOF coatings may be as thick as 12 mm (1/2"). It is typically used to deposit wear and corrosion resistant coatings on materials, such as ceramic and metallic layers. Common powders include WC-Co, chromium carbide, MCrAlY, and alumina. The process has been most successful for depositing cermet materials (WC–Co, etc.) and other corrosion-resistant alloys (stainless steels, nickel-based alloys, aluminium, hydroxyapatite for medical implants, etc.).
Read more about this topic: Thermal Spraying
Famous quotes containing the words high, oxygen, fuel and/or spraying:
“[F]or women, like tradesmen, draw in the injudicious to buy their goods by the high value they themselves set upon them.... They endeavor strongly to fix in the minds of their enamoratos their own high value, and then contrive as much as possible to make them believe that they have so many purchasers at hand that the goods—if they do not make haste—will all be gone.”
—Sarah Fielding (1710–1768)
“All the oxygen of the world was in them.
All the feet of the babies of the world were in them.
All the crotches of the angels of the world were in them.
All the morning kisses of Philadelphia were in them.”
—Anne Sexton (1928–1974)
“The particular source of frustration of women observing their own self-study and measuring their worth as women by the distance they kept from men necessitated that a distance be kept, and so what vindicated them also poured fuel on the furnace of their rage. One delight presumed another dissatisfaction, but their hatefulness confessed to their own lack of power to please. They hated men because they needed husbands, and they loathed the men they chased away for going.”
—Alexander Theroux (b. 1940)
“[Ognev] recalled endless, heated, purely Russian arguments, when the wranglers, spraying spittle and banging their fists on the table, fail to understand yet interrupt one another, themselves not even noticing it, contradict themselves with every phrase, change the subject, then, having argued for two or three hours, begin to laugh.”
—Anton Pavlovich Chekhov (1860–1904)