Session: 03-06 Metals: Mechanical Properties

Paper Number: 93945

93945 - Effect of Heat Treatments on the Structure – Properties of Pbf-Lb/in939 Alloy 

Additive manufacturing of medium and high gamma prime strengthened nickel based superalloys are challenging due to solidification cracking issues and anisotropic properties. This study comprises an understanding on microstructural evolution of powder bed fusion-laser beam (PBF-LB) Inconel 939 alloy after different heat treatments (solutionizing followed by single step aging / two-step aging vs direct aging). The PBF-LB process parameters were optimized to lead to nearly dense coupons (apparent density > 99.9%). Microstructure and mechanical properties were established in two build orientations. Distinct columnar dendritic structures growing across layer boundaries were observed in the longitudinal section of as-built samples, while laser scan patterns and grain boundaries were revealed in the transverse section, without any segregation. A three-stage post build heat treatment cycle employed to solution anneal and age the build coupons, which resulted in the homogenization of the microstructure and precipitation of gamma prime precipitates (Ni₃Al(Ti)). Room temperature and high temperature mechanical properties of the builds indicate a distinct difference in the 0.2% yield strength and ductility with respect to the build orientation and thermal exposure conditions. The precipitation characteristics were compared between the different heat treatments via detailed TEM (transmission electron microscopic) characterization.

Keywords: Inconel 939, Superalloy, Additive Manufacturing, Laser Powder Bed Fusion Laser Beam, Microstructural evolution

Presenting Author: Nandha Kumar Eswaramoorthy Pratt & Whitney R&D Center

Presenting Author Biography: Currently employed as Senior Engineer at Pratt & Whitney R&D Center, Bangalore. I have completed my Doctoral program from Indian Institute of Technology Madras, in the Department of Metallurgical and Materials Engineering. Over there my field of interest was on Welding of similar and dissimilar materials and High temperature deformation behavior of materials especially on creep deformation.

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