Comprehensive assessment of laser powder bed fusion and post-treatments for microstructure and mechanical properties of GH3230 alloy

GH3230 is a solid solution-strengthened material based on a W-Cr-Mo matrix that has been extensively employed in critical hot-end components of aerospace engines. This study offers a comprehensive evaluation of the GH3230 superalloy fabricated using laser powder bed fusion (LPBF) technology, focusing on the optimization of processing parameters, investigating potential cracking mechanisms, and analyzing the microstructural evolution and variations in mechanical properties by post-treatment (solution treatment and hot isostatic pressing). The optimal processing parameters was determined through the application of response surface methodology (RSM) and central composite design (CCD) principles, supported by variance analysis. Under the optimized process parameters (laser power = 250 W, scanning speed = 1040 mm/s, and hatch spacing = 0.06 mm), the alloy is fabricated with a relative density (RD) of 99.62 % +/- 0.04 %. The evaluation of crack sensitivity, based on thermodynamic calculations, indicated that the GH3230 alloy exhibits a high sensitivity to cracking. The analysis of grain boundary (GB) orientation revealed that over 80 % of the cracks occurred at GB angles within the range of 25 degrees to 55 degrees, which are classified as crack-sensitive high-angle grain boundaries. Furthermore, no significant correlation was found between crack length and GB misorientation angle. Due to the combined effects of microstructure and defects, the compressive strength of the solution-treated state (3062 MPa) and the hot isostatic pressing state (3196 MPa) is lower than that of the as-printed state (3308 MPa). This study provides valuable insights into the LPBF processing of the GH3230 superalloy, establishing a solid theoretical and experimental foundation for future advancements in this field.