Producing of low carbon steels having surfaces reinforced with carbide by powder metallurgy technique and microstructure

ABSTRACTMaster ThesisPRODUCING OF LOW CARBON STEELS HAVING SURFACES REINFORCEDWITH CARBIDE BY POWDER METALLURGY TECHNIQUE ANDMICROSTRUCTURESeval Hale MAHMUTOĞLUFırat UniversityGraduate School of Natural and Applied SciencesDepartment of Metallurgical and Materials Engineering2006, Page : 98In the present study, low carbon steel specimens of which surfaces were alloyed with differentamounts of graphite and vanadium carbides have been produced by powder metallurgytechnique. In the study the powder mixtures for surface alloyed side and for low carbon parentmetal were prepared, respectively. To produce surface alloyed side two different Fe-graphitepowder mixtures containing two different amounts of graphite powder (0.6 wt% and 1.2 wt%)with the same amount of vanadium carbide powder changing as 5, 10 , 15, 20 and 25 wt%were prepared. To produce the side of low carbon steel the powder mixture containing 0.2 wt%graphite were prepared. The low graphite powder mixture was filled into the mould first andthe alloyed powder mixture was filled on the low graphite powder and compacted with apressure of 800 MPa at room temperature. After compacting process, the specimens weresintered at 1200 oC for 60 min. After sintering operation, microstructural investigation includingSEM, EDX, elemental mapping and X-ray, and hardness measurements were performed. Fromthe results of microstructural investigation, from the surface alloyed side to low carbon steelside, it was observed four different microstructural regions, namely high alloyed region,partially alloyed region, transient region and low carbon steel parent metal. Especially, carbondiffusion from high alloyed side to low carbon parent metal caused the formation of transientregion .In addition, functionally graded material produced because of carbon diffusion. Fromthe results of hardness measurement, higher values were obtained for vanadium carbide (V8C7)and the hardness values showed a decrease towards the low carbon steel side. As a result, thisstudy showed that surface alloyed and functionally graded materials can be obtained by powdermetallurgy route as shown by microstructural investigations and hardness measurements.Keywords: Surface Composite, Functionally Graded Material, Powder Metallurgy, VanadiumCarbide, Microstructure, Hardness