Experimental study and thermodynamic computational simulation of phase transformations in centrifugal casting bimetallic pipe of API 5L X65Q steel and Inconel 625 alloy

Abstract In this work have been studied the phase transformations occurred during a cladding process by means of centrifugal-casting route used to produce a bimetallic pipe between an API 5L X65Q steel as backing material and Inconel 625 as corrosion resistance cladding alloy. Experimental measurements and computational thermodynamics calculations were developed aiming at characterization and understanding in the clad interphase phenomena. Thermodynamic calculations were performed by Calphad method to obtain pseudo-binary phase diagrams and kinetic simulations, allowing the quantification of interdiffusion phenomena occurred during solidification between the two alloys. Variations of chemical composition and crystallography along interface intended by Calphad calculations were contrasted with chemical microanalysis and nanoindentation measurements, as well as, optical (OM), scanning electron (SEM), and transmission (TEM), and atomic force microscopy (AFM) observations developed through the interface. Results show that a new interfacial region was formed presenting high hardness values with characteristics of a crystallographically transitional region, allowing the clad affixing.