Inconel 625/Al2O3 functionally graded materials manufactured by directed energy deposition

Abstract

Partial repairing using additive manufacturing becomes one of the important issues to provide maintenance, repair, and overhaul service for gas turbine components. Owing to small heat-affected zones, recent additive manufacturing methods enable us to deposit non-weldable Ni-based superalloys on damaged components. Although additive manufacturing can be a strong candidate for the partial repair of Ni-based superalloy components, the repair of thermal barrier coating remains a critical issue in partial repairing. In this study, the feasibility of using directed energy deposition for fabricating an Inconel 625/Al2O3 functionally graded material is investigated. By combining surface forces and convection during deposition, intermixing between Inconel 625 and Al2O3 occurs, resulting in bonding within a functionally graded structure. Both thermal conductivity and flame thermal-gradient test results revealed that the deposited Al2O3 reduces the temperature of IN625 substrate even at 1300 °C environment. Although the omission of bond-coat layer causes a low adhesion strength (8.33 MPa) at the interface between IN625 and Al2O3 deposit layers, the present result represents that directed energy deposition could be an alternative method to achieve thermal barrier coatings on hot components.