Crack-free hard facing options for orifice plate used in oil refinery applications

Abstract

The purpose of this study is to select a suitable tubular wire electrode as an alternative hardfacing material for Stellite 1 in the production of SS304 orifice plates used in oil refineries. It is also intended to develop an efficient deposition procedure for crack-free hardfacing. Compatible cobalt, nickel, and iron-based hardfacing alloys were selected so as to match the hardness and hot hardness properties of stellite 1. Moving heat source analysis was performed to find the heat affected zones and the thermal stress distribution during hardfacing. The significance of weld speed, bead width, and weld concentration on the weld deposition process was analysed using ANSYS, to extract an efficient deposition procedure. The hardfacing alloys were tested for stress and deformation at working temperature (up to 815 οC) to understand the performance. Seven materials were taken into consideration as options along with six parameters. The results revealed a higher longitudinal residual stress of 2000 MPa for Talonite and Tribaloy hardfacing alloys. Colmonoy 6 was found to be having the least stress value of 2186 MPa. Furthermore, the von mises stress values arrived for different conditions showed that the optimal welding condition is 5 mm/s welding speed, 3 mm radius of beam and 455 °C preheat temperature. Microstructural study revealed the dendrite growth in the surface of Colomony 6 hardfacing during solidification, which led to the improvement in mechanical properties.