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现代表面技术表面涂覆技术234567891011121314151617181920212223242526272829303132333435363738394041424344Powderflamespraying:Forthepowderflamesprayingprocess,powderisfeddirectlyintotheflamebyastreamofpressedairorinertgas(argonornitrogen)、Alternatively,Itisimportantthatthepowderisheatedsufficientlyasitpassesthroughtheflame、Thecarriergasfeedspowderintothecentreofanannularbustionflamewhereitisheated、Asecondouterannulargasnozzlefeedsastreamofpressedairaroundthebustionflame,whichacceleratesthesprayparticlestowardsthesubstrateandfocusestheflame、WireflamesprayingInthewireflamesprayingprocess,thewirefeedrateandflamesettingsmustbebalancedtoproducecontinuousmeltingofthewiretogiveafineparticulatespray、Theannularpressedairflowatomisesandacceleratestheparticlestowardsthesubstrate、46505152535456Characteristicsofplasmaspraying:Plasmasprayingproducesahighqualitycoatingbyabinationofahightemperature,highenergyheatsource,arelativelyinertsprayingmediumandhighparticlevelocities,typically200-300m、sec-1、However,someairbeesentrainedinthespraystreamandoxidationofthespraymaterialmayoccur、Thesurroundingatmospherealsocoolsandslowsthespraystream、Vacuumplasma(VPS)orlowpressureplasmaspraying(LPPS)reducestheseproblemsbysprayinginvacuumoralowpressure,inertgasenvironment、Plasmasprayingiswidelyappliedintheproductionofhighqualitysprayedcoatings、5859Principle:isbasicallythesameasthebustionpowdersprayprocess(LVOF)exceptthatthisprocesshasbeendevelopedtoproduceextremelyhighsprayvelocity、ThereareanumberofHVOFgunswhichusedifferentmethodstoachievehighvelocityspraying、OnemethodisbasicallyahighpressurewatercooledHVOFbustionchamberandlongnozzle、Fuel(kerosene,acetylene,propyleneandhydrogen)andoxygenarefedintothechamber,bustionproducesahothighpressureflamewhichisforceddownanozzleincreasingitsvelocity、PowdermaybefedaxiallyintotheHVOFbustionchamberunderhighpressureorfedthroughthesideoflavaltypenozzlewherethepressureislower、Anothermethodusesasimplersystemofahighpressurebustionnozzleandaircap、Fuelgas(propane,propyleneorhyd
