9836

9073

كارشناسي ارشد

شناسايي و انتخاب و روش ساخت مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1393

چهارده، 92ص.: مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

فخرالدين اشرفي زاده، احمد كرمانپور

رحمان حسيني

94/2/1

محمدرضا طرقي نژاد، علي شفيعي

1396/09/26

كتابنامه

مواد

مهندسي مواد

ID9073

93 Effect of grain size on nitrogen diffusion in plasma nitriding of ultrafine nanostructure AISI 304L austenitic stainless steel Hojjat Esfandiary h esfandiary@ma iut ac ir June 10th 2014 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisors Fakhreddin Ashrafizadeh Professor ashrafif@cc iut ac irAhmad Kermanpour Associate Professor ahmad k@cc iut ac irAdvisor Seyed Rahman Hosseini Assistance Professor Hosseinisr@mut es ac irAbstractDiffusion of nitrogen and thickness of nitrided layer in ultrafine and micron grain size AISI304L stainless steel were evaluated in the process of plasma nitriding Improving the surfacehardness of austenitic stainless steels can be obtained by plasma nitriding but operatingtemperature is a limitation of this process for austenitic stainless steels since precipitation ofchromium nitride CrN occurs above 480 C leading to reduction of corrosion resistance AISI304L austenitic stainless steel samples in a range of grain sizes from micrometer tonanometer were produced by severe cold rolling SPD process and reversion annealing ofstrain induced martensite Plasma nitriding was performed at 450 C for 5h and the gascomposition was nitrogen and hydrogen with a ratio of 1 to 3 The evaluation of grain size andobservation of microstructure was performed by scanning electron microscopy SEM andoptical microscopy OM Surface morphology and distribution of precipitates in the structureof plasma nitrided samples were studied by field emission scanning electron microscopy FESEM Energy dispersive spectroscopy EDS was used to obtain the profile ofconcentration of nitrogen and identification of phases before and after plasma nitriding wasperformed by X Ray diffractometer XRD An increase in the thickness of nitrided layerfrom 4 8 to 10 6 m was experienced by decreasing of grain size from 11 m to 135 nm Reduction of grain size led to increasing the penetration depth of nitrogen Theconcentration profiles of nitrogen were consistent with the hardness profiles Grainrefinement enhanced the formation of CrN precipitates as identified by X ray diffractionpatterns Examination of microstructure by FESEM showed that the volume percentage ofCrN in ultrafine samples was higher in comparison to micro grain size samples In additionto the percentage of precipitates the type of phases was significantly affected by the grainsize in plasma nitriding of AISI 304L austenitic stainless steel It was observed that retainedmartensite after reversion annealing caused formation of iron nitride Fe4N in ultrafine grainspecimens Keywords Austenitic stainless steel AISI 304L plasma nitriding cold rolling andreversion annealing grain size diffusion of nitrogen

فخرالدين اشرفي زاده، احمد كرمانپور

رحمان حسيني

محمدرضا طرقي نژاد، علي شفيعي