Determination of mechanical properties of the weld region of iron based T/M materials joined by TIG welding

Nowadays, producing of the powder metal (PM) parts with the powder metallurgy method has gained an importance. The most common advantages of the parts that are produced with this method are fast production ability and that it is not necessary to make other machining processes. Much research has been conducted in the welding of parts produced by other methods and several new welding techniques have been developed. It is hard to weld the powder metal parts because they have porous structure. Therefore, the researches about this issue are very limited. TIG welding method is very common for automotive and aviation industry. In this study, Fe-based powder metal composites were produced using powder metallurgy method under 600 MPa pressure and sintered at 1200ºC. Then, the resulting composites (Fe-C) were welded as PM ? PM, SAE 1020 ? SAE 1020 and SAE 1020 ? PM. These different material compositions were welded with TIG welding method using five different impulses that are 80 A, 100 A, 120 A, 140 A and 160 A. TIG welding has been conducted under argon the protective gas atmosphere. The properties of welded materials were investigated by tensile test, three points bending test, notch impact test and measuring hardness. The metallographic properties of materials were investigated using Optical Microscope and Scanning Electron Microscope. The effects of different welding impulses on mechanic properties and microstructure of the materials were also investigated. As the result of this research, when the impulse of welding increased, generally, the resistance of the samples to tensile and notch impact strength increased. However, bending strength decreased. On the hand, hardness values increased. Fractures generally occurred in heat affected zone at the end of tensile, bending and notch impact tests. Brittle fracture was observed in powder metals whereas ductile fracture was observed in other materials.