Laser Defocusing Effect on the Microstructure and Defects of 17-4PH Parts Additively Manufactured by SLM at a Low Energy Input

In this paper, the microstructure, defects, hardness, and tensile strength of 17-4PH specimens manufactured additively using selective laser melting (SLM) technique were studied. The analyzed parts (10 mm size cubic specimens) with different defocus parameter values (−1, 0, +1 mm) in order to evaluate effect a low power (38 W). study was carried out on three sections each specimen, one perpendicular beam or SLM manufacturing direction (transversal section), another two parallel (longitudinal sections). microstructures an X-ray diffraction technique, as well optical, scanning electron, transmission electron microscopes. Image J software used characterize defects phase ratio. addition, hardness tests performed according corresponding standards. results show that amount austenitic average grain varied defocusing. percentage defective area less than 0.25%. distance did not affect number defects. Adjusting defocusing is important for good mechanical properties.