10996

10127

كارشناسي ارشد

استخراج فلزات

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مهندسي مواد

1394

نه،76ص.: مصور

مهدي احمديان، محمود مرآتيان

حميدرضا سليمي جزي، رحمت الله عمادي

1394/12/04

مهندسي مواد

ID10127

78 Boronizing Heat Treatment of Structure Steel by Boric Acid and Magnesium Mixture and Characterization of the Product Hossein Bahari hossein bahari@ma iut ac ir Date of Submission 2016 01 17 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language PersianSupervisors Mehdi Ahmadian ahmadian@cc iut ac ir Mahmood Mratian meratian@cc iut ac irAbstractBoronizing is a kind of surface hardening thermo chemical treatment in which boron atoms are diffused intoa material surface and produce the hard phase boride In comparison with other treatment this treatment hasadvantages like producting harder phase on material and lower friction coefficient In this study powderboronizing methode was used for boronizing St37 steel Mixed powder was containing boric acid as boronsource and other materials including alumina as as diluents cryolite as activator and magnesium as reducingagent Boronizing was carried out at 900 950 and 1000 C for 2 4 and 6 hours In order to determine phaseformed on the surface X ray diffraction analyse was carried out on a borided sample Then to show texturedboride layer about 30 microns from the surface was removed by emery paper and X ray diffraction analysewas carried out again The results showed that after the treatment Fe2B single layer on the steel surface isformed Also in the following sections of this layer there is texture of the 002 plains Optical microscopyimages of cross sections of samples showed that with increasing duration of treatment from 2 to 6 hours andtemperature from 900 to 1000 C the boride layer thickness increased from 35 to 105 micron Hardnessmeasurements were performed on the cross section of the samples The hardness of boride layers wasbetween 1500 2400 HV and it faced with a sudden drop by moving from the surface to the inside To studyof samples wear resistance wear test was performed on three samples including untreated coated at 900 Cfor 2 hours and coated at 1000 C for 6 hours The results showed that the borided samples weight loss ismuch smaller than untreated sample so that the weight loss of coated sample at 900 C for 2 hours was 20times less than the untreated sample With increasing boride layer thickness the wear resistance increasedsignificantly The coated sample at 900 C for 2 hours in load of 10 kg after 200 meters had about 1 6 mgweight loss while the coated samples at 1000 C for 6 hours in the same load after 1000 meters showedweight loss of about 0 2 mg Keywords Surface treatment Boronizing Acid boric Boride layer Wear

مهدي احمديان، محمود مرآتيان

حميدرضا سليمي جزي، رحمت الله عمادي