Abstract
In this study, AISI 430/AISI 1040 steel couple 10 mm thick were welded in the butt position without any pre-treatment using keyhole plasma transferred arc (KPTA) process. Welded joints were manufactured selecting constant welding speed (0.01 m min^-1) and two different nozzle orifice diameter (2.4 and 3.2 mm), three different welding currents (130, 135 and 140 A), at a constant plasma gas flow (1.2 l min^-1), a shielding gas flow (25 l min^-1). The microstructural changes that occurred in the interface regions of the welded samples were examined by microhardness, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Energy Dispersive Spectrometer (EDS). In order to determine mechanical properties of samples, the V-notch Charpy tests were performed. In addition, fracture types in the notch impact strength tests of samples were determined from the fractographic examinations using SEM.

Key words
plasma transferred arc welding, keyhole, AISI 430, AISI 1040, nozzle orifice diameter

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