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.
Highlights
Power production industries aim at higher power production capacity by increasing the pressure and temperature inside the boilers
Dissimilar joints are made in such a way that, at higher temperature locations 800 alloys are used and in low temperature locations, alloys like P91 are used as they are comparatively cheaper than the 800 alloys
The dimensions of the plates were 200 mm*150mm*4 mm and laser butt welding experiments were carried out using power capacity of 4kW 6-Axis KUKA robot Yb: YAG laser welding solid state laser
Summary
Power production industries aim at higher power production capacity by increasing the pressure and temperature inside the boilers. There is the need for developing new materials to withstand higher temperatures and pressures. They are being continuously developed in order to meet out the requirements of power production industries. Gas Tungsten Arc Welding (GTAW) process is generally used for joining these dissimilar metals and in order to have quality joints between P91 and 800 alloys, the major challenges that. Shanmugarajan et al.[6] studied the metallurgical properties of autogenous laser welded P92 material. With the development of series in 800 alloys called Incoloy 800 HT, it has further widened the possibility of increasing the temperatures and pressures inside the boilers as they have better properties at higher temperatures than 800 alloys. Which are in turn useful for the power plants and some high temperature applications
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