4884

4588

كارشناسي ارشد

خوردگي و حفاظت از مواد

اصفهان: دانشگاه صنعتي اصفهان،دانشكده مواد

1388

ده،122ص: مصور، جدول، نمودار

ص.ع.به فارسي و انگليسي

محمود منير واقفي، احمد ساعتچي

كيوان رئيسي

15/10/88

بهنام لطفي، علي شفيعي

1396/09/22

كتابنامه

مهندسي مواد

ID4588

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

The effect of heat treatment and the electroless Ni P nanocrystalline Coating on the decreasing of damage of austenitic G X40CrNiSi25 12 steel rolls Mohammad Hosein Bina Bina@ma iut ac ir August 8 2009 Department of Materials Engineering Isfahan University of Technology 84156 83111 Isfahan IranDegree M Sc Language FarsiDr Sayed Mahmoud Monir Vaghefi Assoc Prof Supervisor E mail vagh mah@cc iut ac irDr Ahmad Saatchi Prof Supervisor E mail asaatchi@cc iut ac irDr Keyvan Raeissi Assoc Prof Advisor E mail k raeissi@cc iut ac irAbstractIn this research the reason for fracture and destruction of the galvanized furnace rollers of theMobarakeh Steel Company and methods to reduce this problem has been discussed Thisreason was studied by employing chemical analysis metallographic Vickers micro hardness X ray diffractometer and investigations of the crack propagation path in failed sample Theexamination results revealed that the sigma phase embrittlement and an increase ofprecipitations in the microstructure caused the failure In order to reduce the fracture severalcycles of homogenization heat treatment were employed At first impact samples wereprepared from failed rollers and homogenization treatments were carried out at temperaturesranging from 950 to 1100 oC in increments of 50 oC for 2 h then the samples were cooled infour different medias furnace air oil and water After performing the impact test on the heattreated samples in order to investigate the microstructures the sigma phase and precipitationcontents and fractured surfaces optical microscopy metallography X ray and SEMexaminations were performed respectively on fractured samples The roller surfaces failbecause of adhesion so in this research the idea to use Ni P electroless coatings wasintroduced to reduce the adhesion effect Therefore several Ni P coatings containing 6 phosphor with different thicknesses was performed on the surface of the roller s steel Thesamples were placed in an inert atmosphere in 400 oC for 1 hour and in 85 N2 15 H2anneal furnace in 800 oC for 10 hours The effect of anneal furnace atmosphere on themorphology structure variation and abrasion behavior of coatings was studied by performingSEM electron distribution spectroscopy X ray diffraction and the pin on discs abrasion testsin room temperature and 400 oC the results show that the effect of furnace atmosphere on thesamples behavior varies with coatings thicknesses so that a heat treated coating with a 30micron thickness in high temperature abrasion situations and the coatings on the annealfurnace atmosphere in room temperature abrasion situations exhibit excellent abrasionresistance The role of high temperature gas nitriding on cyclic oxidation of the roller s steelwas also studied The results indicated that high temperature gas nitriding process has asuitable and effective influence on the oxidation rate of the roller s steel The low oxidationrate of the nitrided steel after 100 hours of oxidation was because of the appropriate Cr2O3growth due to alloys structure change throughout the nitriding process and the creation of aprotective Cr2O3 layer on Mn15Cr15O4 Key WordsHH Alloy sigma phase embrittlement heat treatment electroless coating high temperaturegas nitriding oxidation

محمود منير واقفي، احمد ساعتچي

كيوان رئيسي

بهنام لطفي، علي شفيعي