The examination of mechanical properties of 4142 steel after surface modification by smelting arc welding (SMAW)

ABSTRACTMasters ThesisTHE EXAMINATION OF MECHANICAL PROPERTIES OF A HEAT TREATED4142 STEEL AFTER SURFACE MODIFICATİON BY SMELTİNG ARC WELDİNG(SMAW)Abdülaziz KOÇFirat UniversityGraduate School of Natural and Applied SciencesDepartment of Metallurgy Education 2007, Page: X+57In this study, on the surface of a 4142 steel a silicon carbid (SiC) powder layer wascoated with use of SMAW (SMAW= Smelting Arc Welding) method with using Citodur 600electrod. As first the specimen thickness was fixed and subsequently the different powderthickness were used. Besides, process parameters such as coating speed, cooling envoriment andwelding current were varied and the effect of these parameters on microstructural chancing,microhardness, macrohardness and abrasive wear resistance of modified materials wereinvestigated.The microstructure of the coating layer was characterized by optical microscope (OM),scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and spectralanalysis. While the hardness of the modified layer was measured by microhardness tester,abrasive wear properties were evaluated under pin-on-disc abrasive wear test conditions. Afterwear tests, wear rates were calculated via the mass losses of the specimens which weremeasured.While the 4142 steel was used as the substrate material, coating powder (SiC) wasalloyed at 0.5, 1 and 1.5 gr weight on to surface of these steel. Effect on the properties of thecoating materials amount of SiC was investigated experimentally. The hypoeutectic andhypereutectic microstructures were observed in coated specimens. Because of rapidsolidification, dendritic phases were formed. The forms of these phases were depended on thecoating speed, the energy input, coolling enviroment and the powder quantity.Coating surface hardnesses values measured between 254-1366 HV. As themicrohardness measurements, the hardness decreased along a line from coating toward tosubstrate material. This can be explained with phase transformations which the coating speed,the cooling enviroment and solidification conditions occured.Wear rates were calculated using mass losses obtained in the result of the abrasive weartest. In surface alloying process used SiC as coating powder, the maximum mass loss was foundby high coating speed, low energy input and low powder quantity conditions. The minimummass loss also was found by low coating speed, and high powder quantity conditions.Keywords: Arc welding, surface alloying, Citodur 600, abrasive wear, silicon carbid (SiC)