Dr. Brahim Belkessa

In this work, incompatible properties of WC-Co cermet and AISI 304 steel were combined in the same component using rotary friction welding (RFW) process. The dissimilar joints were performed using a ductile NiCr interlayer with the change in the WC-Co cermet positioning i.e., fixed rotary side and feeding side. Similar microstructure across the weld joints was obtained of the different welding configurations that produced similar behavior in hardness and elastic modulus. A diffusion zone was formed at the weld interface as a result of the mutual inter-diffusion of both cermet (W and Co) and steel elements (Fe, Cr and Ni) that enhanced with the insertion of the interlayer when the cermet was fixed in rotary side. The introduction of the NiCr interlayer was beneficial to relax the residual stresses and improving the shear strength of the WC-Co cermet/AISI 304L steel joints, which is promising technology for drilling tools industries.

In the present investigation, the influence of heat input on microstructure, residual stresses and corrosion resistance of lean duplex stainless steel welds are discussed. The weldments were made with different heat inputs through changes in welding current and travel speed, using tungsten inert gas process. The microstructural evolution was characterized using optical and scanning electron microscopy, while the residual stresses were measured on surface and thickness by X-ray diffraction technique. The experimental results show significant changes in microstructure and ferrite content with a large fraction of reformed austenite. Samples exhibit compressive residual stresses on the weld surface. Potentiodynamic polarization tests evaluated in 3.5% NaCl solution exhibit high corrosion resistance of the weld metal produced with the low heat input.

This work purposes to investigate the microstructure and the mechanical behavior of dissimilar metals weld between 2205 duplex stainless steel (UNS 31803) and high strength low alloy steel API X52. The joining was produced by shielded metal arc welding process using two different filler metals, the duplex E2209 and austenitic E309 grade.The microstructures of the dissimilar welded joints have been investigated by optical microscopy, scanning electron microscopy and energy-dispersive spectroscopy (EDS). The EDS analysis performed at the API X52/weld metal interface showed an evident gradient of Cr and Ni between fusion and type II boundaries, where the highest Nano hardness value was recorded.