The effect of shielded gases at surface modification of low carbon steel alloys with plasma transfered arc (PTA) method

In this study, low carbon steel surface were alloyed with different ferroalloys powders by using tungsten inert gas (GTA) and plasma transfer arc (PTA) welding processes. During the alloying process of specimens argon gas containing 1-3-5 % N2 was used as shield gas. The microstructures and abrasive wear properties of the alloyed and coated zones were investigated. In the experimental study, plain carbon steel (AISI 1030) surface were alloyed by using Ti, FeMo, FeCrC and Si powders.The microstructure of the coating layer was characterized by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and spectral analysis (XRD). 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. After wear tests, wear rates were calculated via the mass losses of the specimens which were measured.As a result of surface alloying applications using PTA welding processes; modification operation was successfully carried out by using molten powders applied to bottom material surface at each of the two processes.After surface modification by using of PTA process with Ti powders was determined FeTi matrix inside of ferritic microstructure, TiN (1) Obsornite, TiN (2) Titanium Nitride, TiC, ve Fe3C phases were observed. After the surface modification by using of FeMo powder was determined FeMo matrix, FeC, Fe3C, Fe7C3, MoC, MoN ve Mo2N phases were observed inside the residual eutectoid structure formed in microstructure. After the surface modification by using FeCrC powder was determined FeCr matrix, Fe7C3, Cr23C6, CrN, (Fe0,6Cr0,4)2O3 martensite and austenite phases inside the dendritic structure as microstructure were observed. After the surface modification by using Si powders was determined ?-ferrit, SiC and Si3N4 pahses.By increasing N2 ratio in shielding gas rather homogenous and influences microstructure was reached with a resultant hardness increasing which was also monitored. It was observed that the highest hardness and wear resistance among treated specimens were obtained by using shield gas atmosphere of Ar + % 5 N2 within PTA .