Microstructure and mechanical properties of rene 41 alloy manufactured by laser powder bed fusion

Precipitation hardenable Ni-based superalloy Rene 41, considered to have moderate weldability, was produced by laser powder bed fusion (LPBF). Crack-free and dense parts were obtained directly from processing. Parts were characterized in both as-built condition and after aging heat treatment. In the as-deposited condition, scanning electron microscopy and electron back scattered diffraction analysis revealed a fine columnar dendritic microstructure with a preferred orientation along <100>. Transmission electron microscopy analysis revealed the absence of gamma' precipitates in the as fabricated state. After heat treatment, the columnar grain morphology was maintained and formation of distinct carbide particles at the grain and cell boundaries were observed along with the precipitation of fine and homogeneously distributed gamma'. The size of these gamma' precipitates were measured as 8-30 nm which is smaller compared to the reported values in the literature. Significant increase in the micro-hardness value from 347 HV to 548 HV is observed after the heat treatment. Increased room temperature yield and ultimate tensile strength values reaching 857 and 1165 MPa were measured for the samples built parallel to the base plate in the as built state. These values increased to 1263 and 1580 MPa after the heat treatment, ascribed to the presence of fine gamma' precipitates. Fractography analysis revealed that failure occurred in a ductile manner for both as-fabricated and heat-treated samples.