Microstructure and wear behavior of IC10 directionally solidified superalloy repaired by directed energy deposition

Abstract

• The microstructure and wear behavior of different zones of IC10 alloy repaired by directed energy deposition are studied. • The size of primary γ′ phase in HAZ is smaller than that in the substrate, and the size and fraction of γ′ phase are decreased along building direction. • The dominant wear mechanism of the repaired alloy is abrasive wear, and the wear resistance is closely related to the fraction of γ′ phase. Directed energy deposition has been used to repair superalloy components in aero engines and gas turbines. However, the microstructure and properties are generally inhomogeneous in components because of the different processing histories. Here, the microstructures and wear behavior of different zones (substrate, HAZ, and deposit) are investigated for the IC10 directionally solidified superalloy repaired by the directed energy deposition process. It is found that the microstructure of the deposited layers is strongly textured with a <001>-fiber texture in the building direction, and the texture intensity is continuously increased along the building direction. Two kinds of γ′ phase (primary and secondary γ′ phase) can be found in the heat-affected zone (HAZ), and the average size of primary γ′ phase is smaller than that in the substrate due to liquation. In the deposit layers, the size of γ′ phase is much smaller than those in the substrate and the primary γ′ phase of HAZ; both size and the fraction of the γ′ phase decreases with the increase of building height. The wear rate of the substrate is the smallest, indicating the best wear resistance; while the wear rate of HAZ is the largest, indicating the worst wear resistance in the repaired sample. The wear rates in the deposit layers increase from the bottom to the top zones, showing a decreasing wear resistance. Abrasive wear is found to be the dominant wear mechanism of the repaired alloy, and the resistance to which is closely related to the fraction of γ′ phase in the microstructure. The understanding of the influence of microstructure on wear resistance allows for a more informed application of inhomogeneous superalloy components repaired by directed energy deposition in industry.