Powder Synthesis for Cermets on the Base of Induction Heating Technology

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1 Internatonal Scentfc Colloquum Modellng for Electromagnetc Processng Hannover, March 4-6, 003 Powder Synthess for Cermets on the Base of Inducton Heatng Technology A Pechenkov, I Poznak, Yu Udalov, B Lavrov Abstract Carbdes, ntrdes and bordes of metals of IVB and VIB groups of a perodcal law as a sntered producton (cermets) are wdely used n ndustry as a test porton of cuttng tool and other metal-workng tools Tradtonal mult-stages technologes of cermets synthess do not allow reachng of propertes combnaton Synthess process submcron powder mxtures of Al O 3 TN, TN TB, TC TB, SC TB B 4 C s based on nducton heatng technology Some mathematcal approaches to smulate and nvestgate the process are presented n the paper Introducton Carbdes, ntrdes and bordes of metals of IVB and VIB groups of a perodcal law as a sntered producton (cermets) are characterzng by of hgh hardness, chemcal passvty and nfusblty These materals are produced by carbothermcal or plasma chemcal synthess as submcron powder mxtures [, ] Pure monophase carbdes, ntrdes and bordes are as product of synthess n both technologes The powder s exposed by submcron poundng and mxng wth other components Receved mxture s frttng at temperature mo then 500 С Ceramcs, whch are produces by ths way, are wdely used n ndustry as a test porton of cuttng tool and other metal-workng tools Ceramc as a composton of corundum-ttanum carbde - ttanum ntrde s used for cast ron smoothng at speed rotaton more then 50 m/s or t does for cuttng of hardened steels at speed rotaton more then 50 m/s, for nstance Worldwde consumpton of carbde of ttanum, tungsten, zrconum and so on s about 50 t/a (50 mllons of cuttng tools) were realzaton value s $ mllons However, ceramcs, whch are produced by ths way, have low resstance to mpact and hgh cost Besdes, poson gases are generated whch have to be neutralzed durng process Ths crcumstances requres to fnd new technologes of synthess for powders producton havng well capabltes to snterng and resstance to hgh temperature oxdaton The technologes have to exclude or decrease costs of submcron poundng and usng of cheap and non-hazardous prmary raw materals and cheap carbon deoxdzer Synthess technology of corundum - ttanum ntrde mxture from oxdes components n the same technologcal process was an object of nvestgaton Producton of submcron grans of ttanum ntrde, whch are homogeneously dstrbuted between corundum grans, was man goal Carbothermcal deoxdzaton and ntraton of ttanum oxde, whch was mxed together wth corundum, s an dea of technology Corundum lmts of growth of ttanum ntrde grans and the ttanum ntrde grans do not allow snterng of corundum grans [3] Those grans do not allow to growth of each other and prevent of ts recrystallzaton durng of product snterng Crystallne partcles of components are homogeneously allocated and ts szes are less then mcron In ths case the product has hgh mpact elastcty savng 305

2 hgh hardness ( HV), that t s a reason of ncreasng lfe tme of cuttng tools Cost of the ready-made composton s less then the cost of producton of submcron plasma chemcal pure powder of carbdes, ntrdes and bordes Carbonc gas s co-product of suggested technology Installaton and technology Powdered boron carbde was produced by nducton heatng method of mxture of boron oxde and coke [4] It was heated mxture of alunmum oxde, ttanum oxde and carbon n graphte crucble n runnng ntrogen medum to get compost powder Al O 3 TN Common reacton of carbothermc dsoxdaton and ntraton of ttanum oxde can be wrtten as: TO + C + N TN + CO + q Ttanum oxde dsoxdaton can be realzed ether durng drect nteracton between atom of oxygen and ntrogen or through gas phase, or by ths ways smultaneously Equaton of dsoxdaton process through the gas phase s the next: TO + CO + N TN + CO + q Sketch of laboratory nstallaton s presented at fg Power supply s hgh frequency tube generator Advantages of suggested way are nducton method of heat of graphte crucble (reactor) and possblty of smooth control of voltage at nductor It s allows to control of heat temperature Reactor conssts of two coaxal hollow graphte crucbles wth sltted walls, Fg The sltted crucbles are heated fast by nducton method up to requred temperature Internal and external crucbles are heated smultaneously that t s ncreased the heat effcency Moreover, walls slts provde effectve deleton of carbon oxde from reacton space durng of TO deoxdaton and allow to react of ntrogen wth ttanum The basc efforts was drected to solve two problems durng technology mprovement: - producton requred temperature dstrbuton n powder mxture to start synthess process; - defnton of changng low of power sources n graphte reactor to keep synthess process Fulfllment of the frst condton provdes homogeneous dstrbuton of Al O 3 and TN phases n the volume of syntheszed product Carbothermcal deoxdzaton ttanum oxde s accompaned by heat generaton and mxture oxdes temperature can be ncrease The mxture components can be melted and synthess of TN wll de Second condton provdes realzablty of the sold phase synthess Numercal tools and base equatons Investgaton of physcal-chemcal processes on the base of mathematcal modelng requres to solve equatons whch descrbe electromagnetc and transtonal thermal phenomena It takes to account both electrcal and exothermal reacton heat sources Moreover, currents spread character n the segments of graphte crucble requres solvng of 3D equatons of electromagnetc feld 306

3 Ntrogen on Quartz chamber Sltted graphte crucble Inductor Alumnum oxde - ttanum oxde mxture Carbonc oxde Fg Sketch of the lab nducton furnace Fg Sltted graphte reactor Experence of numercal nvestgatons of electromagnetc felds of nducton systems wth sltted metallc crucbles for oxdes meltng shown that for suggested process t can be used D mathematcal model [5, 6] Electromagnetc model based on combned approach Interor problem of computaton of electromagnetc feld n the load s solved by fnte element method (FEM) and exteror problem s solved by ntegral equaton method (IEM) Influence of sources (nductor current) s takng nto account by means of ntegral equatons Ths approach allows to get dstrbuted parameters n the nvestgatng system wth a lot of fnte elements and short tme of calculaton Accordng to the secondary sources method [7] electromagnetc feld n conductve regon s calculated usng conducton currents Internal problem s solved by D dfferental equaton relatve vector magnetc potental by FEM [8] Transent electro-thermal mathematcal model n generally accepted terms s descrbed by the next equaton system: + jω σ j E j M jds + jω S S k k ( M M ) π R E σ E ds = U, A A A A jωσ A µ + + =, 0 R R R z R T T T C v = λ + λr + q, t z z R R R k l wth boundary condtons for thermal problem: 4 4 ( T T ) + α( T T ) T λ = εσ c c R 307

4 Soluton of the equatons system s complcated by nonlnear coeffcents and boundary condtons n the equatons 3 Numercal and expermental results Numercal nvestgaton of electromagnetc and thermal felds n the nducton system allowed to defne requrng temperature dstrbuton n the graphte reactor and powder and changng voltage low at nductor The defned changng voltage low provdes needed synthess process condtons Heat sources and temperature dstrbuton n graphte reactor are shown on Fg 3 and Fg 4 Workng nducton furnace and ttanum ntrde whch was produced by ths technology (Fg 5 and Fg 6) z r Fg 3 Heat sources dstrbuton Fg 4 Temperature dstrbuton Fg 5 Workng nducton furnace Fg 6 Ttanum ntrde 308

5 Conclusons Elaborated technology allows to produce submcron cermets powder from metals oxdes of IVB and VIB groups of a perodcal law and cheaper carbon deoxdzer The powders have well capabltes to snterng and resstance to hgh temperature oxdaton The snterng materals were tested to abrasve ablty and sngle gran strength followng Russan standards Abrasve ablty of the materal s better then standard specmen n one and half tmes Sngle gran strength s better then standard one n two tmes References [] Patent of USA 4589 Patentee Boca Raton, Florda, USA [] Patents of USA , Patentee PPG Industres Inc, USA [3] Yudn B F, Mnatsakanyan E D, Ordanan S S Thermodynamc analyss of nteracton n TN Al O 3 sstem J of Appled Chemstry 98 Vol 55 P 03 [4] Tumanov Yu N Electrothermal reactons n modern chemcal technology and metallurgy Moscow Energozdat, 98 (n Russan) [5] Poznak I, Pechenkov A Specal tools for nvestgaton and controllng of nducton skull meltng processes Proceedngs of the Internatonal Colloquum "Modellng for Savng Resources", Latva, Rga, May 00, pp [6] Poznak I, Pechenkov A An Approach of Electrcal Conductvty Estmaton of Techncal Materals Melts 8 th Internatonal Conference on Mcrowave and Hgh Frequency Heatng Bayreuth, Germany, September, 3-7, 00 [7] Nemkov V, Demdovch V Theory and calculaton of devces of nducton heatng Lenngrad Energoatomzdat, 988 (n Russan) [8] Char "Fnte Element Soluton of the Eddy Current Problem n Magnetc Structures", IEEE Trans Power App & Syst, Vol Pas-93, Jan/Feb 974, pp 6-7 Authors Dr Pechenkov, Andrey Department of Electrotechnology St Petersburg's Electrotechncal Unversty Prof Popov str, , St Petersburg, Russa E- mal: aypechenkov@maleltechru Prof Udalov, Yur Department of Electrotechnology and Plasmachemstry St Petersburg's Insttute of Technology Moskovsky pr, , St Petersburg, Russa E- mal: udalov@peterlnkru Dr Poznak, Igor Department of Electrotechnology St Petersburg's Electrotechncal Unversty Prof Popov str, , St Petersburg, Russa E-mal: vpoznak@maleltechru Dr Lavrov, Bors Department of Electrotechnology and Plasmachemstry St Petersburg's Insttute of Technology Moskovsky pr, , St Petersburg, Russa 309