Investigating an API X65 steel pipe cladded with alloy 625

Abstract

Pipes (rigid risers and flowlines) are employed to transport oil and gas from the wells to the platforms. In these pipes, the fluids can be very corrosive and, therefore, corrosion-resistant alloys (CRA) must be chosen. Alloy 625 is a well-known CRA with improved corrosion resistance. However, nickel-based alloys have high cost compared to that of the low alloy steels, thus pipes entirely made of CRA are economically unfeasible. Internal coating with a thin CRA layer is a less expensive and suitable alternative than the solid CRA. An internal coating by overlay manufacturing process can induce phase transformations at the interface. In this work, an alloy 625 cladding layer was deposited in an API X65 steel substrate with an automatic weld overlay system using gas tungsten arc welding (GTAW) process (often referred to as tungsten inert gas (TIG) hotwire). Thus, this study aims at evaluating an API X65 steel pipe cladded with alloy 625. The results show a suitable nickel-based alloy overlay deposited in an API X65 carbon steel substrate.