Subcategory: Materials Science
Kevin Thompson - Dillard University
Army is interested in additive manufacturing (AM) to alleviate logistics issues on the battlefield. Powder bed fusion is a type of AM processing where rapid melting and solidification occurs when a highly-focused laser beam irradiates the powder bed. The laser parameters have a strong effect on the thermal history, which in turn influences the microstructure. 17-4 (PH) is a commonly known martensitic precipitation hardened stainless steel. It contains approximately 15-17 percent chromium, 3-5 percent nickel, and 3-5 percent copper. The hypothesis that exposing this material to intense laser beam will increase the its strength, hardness, and corrosion resistance and machinability The thermal behavior of wrought 17-4 subjected to a laser beam was investigated through experiments to develop a simulation for predicting optimal laser parameters. Single line welds were produced on a 17-4 (PH) stainless steel plate irradiated by a laser beam operating at powers of 100(w), 150(w), 200(w) 300(w), and 400(w). The speed of the laser beam was set at 6.25 mm/s, 12.5(mm/s), 25(mm/s) and 50(mm/s). The plate is then sectioned and etched to reveal melt pool boundaries and heat-affected zones (HAZ). Thermocouples nominally placed 4 (mm) below the surface of 17-4 (PH) at various depths, were used to measure temperatures as the laser irradiated across. For the simulations, transient temperature fields are calculated in the plate using commercial finite element code measurements (FEM) that considers temperature-dependent thermophysical properties. Preliminary simulation results revealed good agreement between measured and predicted temperature results. The FEM reduces the number of physical prototypes and experiments and optimizes components to help eliminate distortions. The data unveiled in the thermocouple experiments verified (F.E.M) modules. There was a strong relatability between 17-4 (PH) melt pool affected heating zones and the radiated heat conduction through the stainless steel plate.
P. Wanjara and M. Jahazi, Canadian Metallurgical Quarterly, vol. 48, issue 3, 2009, pp. 317-26
Funder Acknowledgement(s): Daniel Galles
Faculty Advisor: Dr. Abdalla Darwish, Adarwish@dillard.edu
Role: I conducted the Laser Welding and created the finite element simulation