6364

396 دكتري

دكتري

مهندسي مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1390

سيزده،168ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

مرتضي شمعانيان

احمد ساعتچي

29/8/90

فرشيد كاشاني بزرگ، عليرضا صبور روح اقدم، حسين ادريس

مهندسي مواد

ID396 دكتري

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

AbstractThe main goal of this study is to fabricate Mo Si B based claddings containing Mo5SiB2 on nickel substrateusing tungsten inert gas surfacing process in order to improve oxidation resistance of Ni In this regard thecladding procedure was performed in different manners using elemental powders elementalpowders molybdenum interlayer and alloyed powders molybdenum interlayer The results showed that in theabsence of molybdenum interlayer the chemical composition of cladding was strongly changed due to dilutionwith substrate The use of two molybdenum interlayers reduced dilution significantly The phase evolutionduring cladding procedure is significantly dependent on conditions of feedstock powders In the case ofunmilled powders the desirable Mo5SiB2 phase was not formed in the clad worthwhile Mo2Ni3Si and Mo5SiB2phases were formed after using alloyed powders To produce alloyed Mo Si B powders the mechanical alloyingand subsequent heat treating process were performed After investigation on Mo Si B system two kinds ofpowder mixtures including Mo 12 5Si 25B P1 and Mo 25Si 10B P2 at were selected as referencepowder mixtures In addition four other powder mixtures were considered by decreasing molybdenum contentof reference powder mixtures in a Si B constant ratio It was indicated that phase evolutions during mechanicalalloying and subsequent heat treatment of P1 powders depends on milling conditions milling time and also timeof heat treatment Finally 20h milling and subsequent annealing for 5h at 1100 C led to formation of variousMo Si B alloyed powders containing Mo5SiB2 phase Phase types of these powders were dependent oncomposition of powder mixtures Weld cladding of alloyed powders led to formation of a multi phase claddingsconsisting of Mo5SiB2 Mo2Ni3Si matrix phase It was also indicated that microstructure and phase compositionof claddings depends on phase structure of feedstock powders The results of oxidation tests at 1000 C showedthat the presence of Mo5SiB2 improves the oxidation resistance of claddings while its effect depends onmicrostructure and composition of claddings Although the cladding produced using P1 based powderscontained Mo5SiB2 but the multiphase structure of claddings including nonresistant phases such as Mo2Bresulted in spallation of oxide films comprised of complex compounds In contrast the presence of continuous Mo Ni 5 Si B 3 phase in microstructure of claddings produced by P2 based powders led to formation of SiO2protective layer on the surface during oxidation procedure Here these claddings exhibited excellent oxidationresistance at high temperatures Keywords Weld Cladding Mo Si B Mo5SiB2 Mechanical alloying Microstructure Oxidation

مرتضي شمعانيان

احمد ساعتچي

فرشيد كاشاني بزرگ، عليرضا صبور روح اقدم، حسين ادريس