5352

315 دكتري

دكتري

مواد

اصفهان: دانشگاه صنعتي اصفهان،دانشكده مواد

1389

سيزده،252ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

فخرالدين اشرفي زاده

احمد كرمانپور

4/5/89

محمد حسين شريعت،سعيد رستگاري،محمدعلي گلعذار

مهندسي مواد

ID315 دكتري

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

The formation microstructural evaluation and high temperature behavior study of Al Ti coatings on nickel based superalloy B 1900 Abstract In the current investigation attempts have been made to introduce titanium in the aluminide coating on B 1900 nickel base superalloy via conventional or innovated techniques Coating application methods included co diffusion of Al and Ti in a powder mixture sequential diffusion of Ti and Al in separated powder mixtures and finally diffusion annealing of cold sprayed mixture of Al and Ti The coatings obtained were characterized by optical and electron metallography EDS microanalysis depth profiling via glow discharge optical emission spectroscopy and X ray diffraction for phase analysis Based on the microstructural features the formation mechanism of the coatings were determined The results proved that sequential and co diffusion of Al and Ti can form aluminide coatings with considerable amounts of Ti incorporation but other processes were not able to produce modified aluminide coatings on B 1900 alloy The microstructure of modified coatings included distinct NiAl layer and ternary Al Ni Ti compounds such as Al2NiTi AlNi2Ti and Al1 XNiX 3Ti High temperature behavior of Ti modified aluminide was compared with simple aluminide and CoNiCrAlY overlay coatings The results showed that cyclic oxidation resistance of Ti modified aluminide coatings in one hour cycles at 1100 C was inferior compared to simple aluminide coating but the reverse was observed for 10 hour cycles at the same temperature Kinetic study of cyclic oxidation behavior of Ti modified aluminide coatings with one hour cycles at 1100 C revealed the growth rate of oxide scale was comparable to aluminum oxide growth rate Similar microstructural changes due to oxidation with 10 hour cycles were observed in all of the coatings including martensitic and diffusional transformation in NiAl phase of the coatings Titanium did not show any positive effect as an inhibitor to these transformations The hot corrosion behavior of Ti modified aluminide coatings at 900 C with 1 mg cm2 sodium sulfate deposition repeated every 32 hours were superior to simple aluminide coating and inferior to CoNiCrAlY overlay coating Titanium did not change the hot corrosion mechanism but retarded its propagation Hot corrosion led to crevice formation and coating spallation in some areas of all diffusion coatings and blister formation in simple aluminide coating Based on the microstructure of corroded specimens a mechanism was proposed for hot corrosion of the coating Key words Ti modified coating co diffusion titanizing cyclic oxidation characterization hot corrosion crevice

فخرالدين اشرفي زاده

احمد كرمانپور

محمد حسين شريعت،سعيد رستگاري،محمدعلي گلعذار