Browsing by Subject "laser powder bed fusion (L-PBF)"
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Item The Effect of Heat Treatment on the Microstructure and Tensile Properties of Laser Powder Bed Fused (L-PBF)(2022) Baig, Shaharyar; Shao, Shuai; Gradl, Paul R.; Shamsaei, NimaThe as-fabricated microstructure of Haynes 214 by laser powder bed fusion (L-PBF) is dendritic due to the high cooling rates, which is generally considered undesirable and removed via heat treatments. In this study, the effects of various heat treatments on the microstructure and tensile properties of laser powder bed fused Haynes 214 are investigated. Test specimens were fabricated on a L-PBF system in the vertical orientation. Multi-step heat treatments were performed including stress-relief, hot isostatic pressing, solution annealing and ageing. Examining the microstructures revealed columnar grains in the non-heat treated (NHT) condition with grain growth occurring after stress relief. Room temperature tensile tests showed the lowest strengths in the NHT condition. The highest strengths were seen in the aged condition which was attributed to gamma prime precipitation hardening. Finally, the tensile fracture surfaces indicated ductile failure mode in both the NHT and heat treated conditions with the measured elongation being the highest for NHT and lowest in the aged condition.Item In-Process Monitoring of Cross Contamination in Laser Powder Bed Fusion (L-PBF) Additive Manufacturing (AM)(University of Texas at Austin, 2016) Jamshidinia, M.; Boulware, P.; Marchal, J.; Mendoza, H.; Cronley, L.; Kelly, S.; Newhouse, S.Cross contamination in laser powder bed fusion (L-PBF) Additive Manufacturing (AM) could locally change the chemical composition and stress distribution in a component. It also could result in the formation of flaws, and consequently lower the mechanical performance of a component. In this study, the in-process monitoring and detection of cross contamination was investigated in L-PBF process, also known as direct metal laser sintering (DMLS). A setup was designed and fabricated at EWI, where contaminant materials could be introduced on the powder bed without interrupting the fabrication process or breaking the chamber environment. Tungsten particles were used as the contaminant material, in the matrix of Inconel 625. Six levels of contamination were calibrated, and were introduced in two static and dynamic modes. Photodetector, spectrometer, and optical camera were used for the data acquisition. One of the sensors showed the most promising results. X-ray computed tomography (CT) and optical microscopy were used to validate data collected by the sensors.Item Microstructural Characterization of Laser Powder Bed Fusion (L-PBF) Additively Manufactured Inconel 718 for Aerospace Application(2022) Doris, A.; Trujillo, L.; Godinez, Dana; Arrieta, E.; Wicker, R. B.; Gradl, P.; Medina, F.Alloy 718 (Inconel 718) is used for aerospace applications because of its excellent corrosion resistance and mechanical properties. This alloy is particularly applicable in manufacturing components subjected to high temperatures in rocket engines, aero-engines, and gas turbines. Properties for this alloy when processing on systems from similar and different Laser Powder Bed Fusion (L-PBF) machines provide subtle differences due to process parameters, feedstock, and machine configurations. A series of sixteen L-PBF AM Inconel 718 geometric feature build plates have been evaluated for microstructure using optical microscopy. This study presents the details of the microstructure analysis concerning geometry and different machine platforms. Microstructural investigations of these samples included average grain width measurement for all the X-Y and Y-Z build layers and are accompanied by process parameters and powder characterization. The present work concludes with a discussion on the importance of captured differences among builds to understand the practical limitations among AM platforms.Item Microstructure and mechanical properties of additively manufactured Inconel 718: A comparative study between L-PBF and LP-DED(2022) Ahmad, Nabeel; Baig, Shaharyar; Ghiaasiaan, Reza; Gradl, Paul R.; Shao, Shuai; Shamsaei, NimaThis study aims to characterize the microstructure and mechanical properties of Inconel 718 fabricated using two different additive manufacturing processes: laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED). Similar heat treatments (HTs) including stress-relief (1065ºC for 1.5 hr), hot isostatic pressing (1162ºC under 100 MPa isostatic pressure of Ar gas for 3 hr), solution annealing (1065ºC for 1 hr), and two-step ageing (760ºC for 10 hr + 650ºC for 10 hr) are applied to both batches. Scanning electron microscopy is utilized to characterize microstructural evolution during each step of HTs for both samples. Tensile tests are performed to evaluate the mechanical properties at room temperature. Elongation to failure of L-PBF specimens is measured to be 16% lower than that of the LP-DED ones, while the ultimate tensile and yield strengths of L-PBF specimens are, respectively, 9% and 6% higher, compared to the LP-DED ones. The differences in tensile properties between two specimens are explained using microstructural and fracture surfaces analysis.