9360

8642

كارشناسي ارشد

مواد-شناسايي و انتخاب مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1393

دوازده،76ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

علي شفيعي

كامران اميني

23/9/93

محمود منير واقفي، حميدرضا سليمي جزي

مهندسي مواد

ID8642

Investigation the effect of deep cryogenic treatment on microstructure and tribological behavior of tool steel H13 Mehran Hosseinizadeh m hosseinizadeh@ma iut ac ir September 21 2014 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Language FarsiDegree M Sc Supervisor Dr Ali Shafyei shafyei@cc ac iut irAbstractIncreasing the amount of carbon and alloy elements in steels causes reduction in the start and finishtemperatures of martensitic transformation Therefore in steels with high carbon and alloyelements the finish temperature of martensitic transformation decreases to lower than 0 C Afterusual heat treatment of quenching and tempering some austenite will remain in steel structure Thepresence of austenite causes reduction in hardness wear resistance and dimensional stability ofsteels Thus one of the major challenges in the heat treatment of these steels is minimizing oreliminating the amount of retained austenite One of the methods can be used for this purpose isdeep cryogenic treatment After performing usual heat treatment on H13 tool steel some austenitewill remain in structure Considering the widespread usage of this steel it seems to be necessary touse deep cryogenic treatment in order to reduce the amount of retained austenite In this study using metallography and optical microscopy the effect of keeping samples in 196 C for 24 48and72 hours respectively was investigated In addition the amount of hardness and wear resistancewas studied using hardness tests and wearing tests and finally wearing mechanism was studiedusing electron microscopy After quenching and tempering the amount of retained austenite wasabout 7 while this percentage decreases to lower than 1 after deep cryogenic treatment for 72hours Results indicated that the mechanical properties such as hardness and wear resistanceincreases after keeping samples in 196 C for 72 hours as 8 and 43 respectively The increasein mechanical properties was due to reduction in the amount of retained austenite and etha carbidesprecipitation in microstructure Evaluation of wear surfaces and debris particles caused revealedthat in usual heat treatment of quench and temper the dominant mechanism was extreme adhesivewear and in deep cryogenic treatment the dominant mechanism was weak adhesive wear andtribochemical Key wordsdeep cryogenic treatment H13 tool steel wear behavior retained austenite

علي شفيعي

كامران اميني

محمود منير واقفي، حميدرضا سليمي جزي