Mechanical and Metallurgical Characterization of Laser Welding on P91 Ferritic Steel and Incoloy 800HT Dissimilar Joints

Abstract

In this work, microstructural characterization and mechanical properties of P91 and Incoloy 800HT dissimilar laser beam welded joint were analyzed. In addition to that, metallographical studies were conducted using Optical microscopy, Scanning electron microscopy (SEM) equipped with Energy-dispersive X-ray spectroscopy (EDX) and X-Ray diffraction analysis (XRD). Effect of specific point energy on weld microstructure was predicted and it was compared with fusion zone hardness. The δ-ferrite content of the welds was predicted and it was correlated with the results measured by ferritoscope. Increase in heat input led to a minimal increase in the weld bead width and also the depth of penetration as predicted by microstructural studies. The traces of δ-ferrite in the interface of P91 side led to higher strength and microhardness of the weld. Failure of tensile specimens in the HAZ of Incoloy 800HT side was because of lower ferrite content (0 to 0.36) in that region and also due to the presence of the brittle intermetallic phases. The tensile strength of higher specific point energy welds was greater compared to other welds because of precipitation hardening and presence of δ-ferrite. Fractography results of fracture surfaces contain uniform dimples which showed that the failure took place in a ductile mode.

Study on Microstructure and Mechanical Properties of Laser Welded Dissimilar Joint of P91 Steel and INCOLOY 800HT Nickel Alloy

“…The yield strength of the welded joint was measured as 265 ± 4 MPa and 297 ± 5 MPa for the AW and PWHT joint, which was close to the yield strength value of the Incoloy 800HT base metal (285 ± 4 MPa). Base metals exhibited the highest tensile and yield strength, while the welded specimens have shown resembling results, which are reported in another study [ 48 ]. For a sub-size specimen, the fracture was observed in the center region of the WFZ, and the strength was measured as 565 ± 5 MPa and 549 ± 4 MPa for AW and PWHT conditions, respectively.…”

On the Use of Laser Beam Welding for Austenitic Stainless Steel Type 316L and Stainless Steel Type 304 for Aerospace Applications.

“…The macro welded sample gave a maximum tensile strength of 582.753 MPa at a load of 20.922 KN, welded with a power of 1800 Watt. The macro welded sample is shown in Figure 5 [11,12]. When the laser beam welded samples were heated the grain structure changed within the weld zone.…”

Butter-weld Interface Microstructural Analysis Employing NCS and LAMS Sections

“…The application of dissimilar welded joints is present in the power generation, petrochemical and transformation industries [1][2][3][4][5] . In the oil and gas extraction system, mainly offshore, these joints are subjected to very unfavorable working conditions, both in terms of oxidation and embrittlement and high pressures [6][7][8][9] . These conditions have demanded the adoption of materials and manufactoring processes that allow better mechanical properties and a lower sensitivity to the presence of hydrogen 10,11 .…”