A Methodology for Predicting Surface Crack Nucleation in Additively Manufactured Metallic Components
- PDF / 1,251,741 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 66 Downloads / 180 Views
ODUCTION
IN recent years, there has been great interest in the production of reliable and damage-tolerant metallic components using additive manufacturing (AM) techniques. In these rapid prototyping manufacturing processes, metallic components are fabricated via layer-by-layer deposition and fusion of powders to the required shape using three-dimensional (3D) part profiles generated by computer-aided design model.[1] This class of manufacturing techniques, often referred to as 3D printing, includes additive layer manufacturing (ALM), selective laser melting (SLM), solid free-form fabrication, and direct metal laser sintering (DMLS).[1] Advances in AM techniques have produced parts that are near net-shape with mechanical properties that are
KWAI S. CHAN is with the Southwest Research Institute, San Antonio, TX, 78238. Contact e-mail: [email protected] ALONSO PERALTA-DURAN is with Honeywell Aerospace Inc., Phoenix, AZ, 85072-2181 Manuscript submitted February 19, 2019. Distribution A: Approved for public release, distribution unlimited. Article published online June 21, 2019 4378—VOLUME 50A, SEPTEMBER 2019
comparable to, or even exceed those of, conventional wrought alloys.[2] Despite these advances, applications of critical metallic structural components made by AM processes are still rare because of the lack of a robust methodology for qualifying the reliability and certifying the damage tolerance performance of AM materials and parts.[2] One of the important challenges to quantifying the reliability of critical AM components is that variations in AM-processing parameters such as power input, build rate, scan rate, beam width, layer thickness, and powder size would lead to variations in local microstructure, properties, internal anomaly, and surface irregularity. These location-specific microstructures and irregularities determine the material properties, fatigue characteristics, and therefore the reliability of the AM component during service.[3–15] Internal anomalies in AM materials may include pores and unmelted powders formed between layers and aligned along the interlayer direction. Formation of these anomalies, which have been attributed to non-optimized build parameters,[7,9] may be controlled or reduced by altering the build parameters to optimize the relevant processing conditions, e.g., increasing the current density.[9]
METALLURGICAL AND MATERIALS TRANSACTIONS A
Surface irregularities or rough surfaces in ALM materials have been attributed to several sources,[16,17] including stair-stepping, balling, and the attachment of partially bonded surface particles. The surface topography is particularly important for the fatigue performance of parts intended for use in the as-built, net-shape condition when surface finishing or machining may not be desired or practical.[2] Recent studies indicated that a rough surface finish can reduce the fatigue life of Maraging 300 steel,[18] Ti-6Al-4V,[19,20] Alloy 718,[21] and Alloy 718Plus specimens[22] fabricated by AM techniques. X-ray micro-CT imaging of the AM mater
Data Loading...
