10454

9649

كارشناسي ارشد

جوشكاري

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مهندسي مواد

1394

سيزده، 74ص.: مصور، جدول، نمودار

مهدي صالحي، حميدرضا سليمي جزي

علي اشرفي

1394/07/04

مهران نحوي، بهروز موحدي

1396/10/04

كتابنامه

مواد

مهندسي مواد

ID9649

به فارسي و انگليسي

75 Effect of cladding powder composition on microstructure and mechanical properties of the clads obtained on 304SS using GTAW process Seyed Javad Tondpour j tondpour@ma iut ac ir 2015 07 13 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Mehdi Salehi Professor surfacesalehi@hotmail com Hamid Reza Salimi Jazi Associate Professor hrjazi@cc iut ac irAbstractOne of the most usual processes in surface engineering is cladding of the surface ofcomponents Since the major destruction mechanisms of components are usually beginsfrom the surface therefore protection and strengthening of their surfaces are vital andcrucial issues in determination of the quality and durability of components andconsequently the performance of the manufacturing unit and the final cost of products Forthis purpose in the present study cladding of the 304 stainless steel by molybdenum andchromium and its effect on the microstructure and hardness of the cladded layer wasinvestigated In this regard by simultaneous synthesis of molybdenum from molybdenumtrioxide and chromium from chromium oxide the elements were provided on the clad Thecladding was also performed both with and without the presence of potassiumpermanganate and carbon For this purpose 304 stainless steel specimens were cladded bygas tungsten arc welding method To do this powder mixture containing chromium oxide molybdenum trioxide and nickel with various amounts of potassium permanganategraphite as the source of carbon were prepared with appropriate stoichiometric ratio andmilled Then the sodium silicate binder was added to the mixture and the resulting pastymixture was applied on the surface of the specimens as a pre placed past After drying inthe air and oven the cladding was carried out using GTAW The cross sections of claddedsamples were studied by optical microscopy OM and scanning electron microscopy SEM The results revealed that microstructure of the weld zone consisted of austenite andferrite which formed during the solid state transformation of primary ferrite to austenite inthe cooling cycle so that the morphology of ferrite in the center of the weld was lathyferritic in austenite matrix which changed to skeletal ferrite in the interface of the substrateand clad It was also found that addition of potassium permanganate to the preset pastelayer increased the temperature of weld pool which enhanced the synthesis ofmolybdenum and chromium and resulted in the increase in the amount of ferrite in themicrostructure of the cladded layer X ray diffraction was used to study the phasecomposition of cladded layers Presence of the Cr1 36Fe0 52 FeMo and MoNi4 peaks in thediffraction patterns of the cladded specimens showed that molybdenum and chromium wassynthesized in the weld pool The microhardness profile of cladded samples demonstratedthat the maximum value of hardness in the cladded layers was changed from 230 HV forthe sample without potassium permanganate and graphite to 302 HV for the samplecontained 3 moles of potassium permanganate and 5 moles of graphite The value ofhardness decreased by increasing the distance from the weld center due to the decrease inthe amount of ferrite Keywords Synthesis 304 stainless steel Lathy ferrite Skeletal ferrite Cladding Gas tungsten arcwelding

مهدي صالحي، حميدرضا سليمي جزي

علي اشرفي

مهران نحوي، بهروز موحدي