The determination of welding zone mechanical properties of ferrous based P/M metarials joined by laser welding

Production of machine parts using powder metallurgy has gained a lot of importance in recent years. Fast production capacity and the fact that produced parts do not need machining processing are significant advantages of this technique. Much research has been conducted in the welding of parts produced by other methods and several new welding techniques have been developed. Powder metals are not easy to weld because they have porous structure. Therefore, there has been limited research addressing this issue. The appropriate welding technique is determined by the type of powder metal, production method, and other material properties. Laser welding is a novel welding technique that offers several advantages. In this study, Fe-based powder metal composites were produced by powder metallurgy under 600 MPa pressure and sintered at 1120 0C. Then, the resulting composites (Fe-Graphite) were welded with powder-powder, ferrous-ferrous with SAE 1020, and powder-metal with SAE 1020. Different material compositions and different welding speeds of 0,5, 0,6, 0,7, 0,8, 0,9 m/min using CO2 laser welding method were used in the study. Laser welding was carried out in laser welding device having a power of 2500 W and diameter nozzle of 18 mm, values of focus 175 mm and under argon gas environment. The properties of welded materials were investigated by measuring hardness, tensile, three point bending and notch impact tests. The metallographic properties of the materials were investigated using Scanning Electron Microscope and XRD. The effects of different laser welding speeds on the mechanical properties and microstructure of welded materials were also investigated. As laser welding speed increased, the resistance of the samples to tensile, bending and notch impact strength decreased. On the other hand, hardness values increased. Fractures occurred in main material in the tensile test, but occurred in heat affected zone (HAZ) at the end of bending or notch impact tests. Brittle fracture was observed in powder metals whereas ductile fracture was observed in other materials.