Laser powder bed fusion of compositionally graded CoCrMo-Inconel 718

Abstract

Manufacturing of compositionally graded alloys (CGAs) using powder bed based additive manufacturing (AM) techniques such as Laser powder bed fusion (LPBF) poses challenges in terms of achieving homogeneity in terms of mixing of the constituent alloys, their unintended segregation and formation of unwanted brittle phases. In this study, a novel method for LPBF of large-scale compositionally graded alloy components with continuous compositional variations across their length was devised and demonstrated by producing CoCrMo-Nickel based superalloy CGA coupons that are defect-free and with smooth end-to-end variations in the composition and microstructures. The variations in the tensile properties and hardness, measured using high throughput characterization techniques, were rationalized by recourse to the different phases present in the microstructures. The method has the potential to be extended to other material combinations for creating high quality CGA components. • A new method to fabricate compositionally graded alloys using the selective laser melting technique is demonstrated. • A compositionally graded alloy with CoCrMo and IN718 at either ends with minimum porosity was built and characterized. • Smooth and continuous variations in the chemical compositions and mechanical properties were observed. • The variations in the mechanical properties along the gradient direction are correlated with the microstructural features.