Product Code: JLA_17_1_47
Andrew J. Pinkerton
School of Mechanical, Aerospace, and Civil Engineering, The University of Manchester, Sackville Street, Manchester, M60 1QD U.K.
Use of the high powered diode laser (HPDL) for direct metal deposition enables multiple layer cladding to be performed with a nominally rectangular beam, traversed at different angles to the fast axis, or with a fiber-coupled, circular beam. These factors may provide an advantage over the traditional beam profiles of CO2 and Nd:YAG lasers, so there is a need to examine the effect that they have on the process and final product characteristics. This article reports such an examination. A 1.5 kW HPDL and 316 L stainless steel powder are used to experimentally investigate the dimensions, microstructure, surface finish, and hardness of multiple layer walls produced using nominally rectangular and circular beams under a range of conditions. The diode beam profiles are modeled using a “Gaussian beam array” method for the nominally rectangular beam and a “concentric series” method for the fiber-coupled beam. Quasistationary state temperature profiles are produced for both beam shapes by superposition of Gaussian source solutions. The experimental results show little difference in microstructural properties, elemental composition, or hardness due to beam shape or traverse direction, but track dimensions are dependent on beam geometry. Wall width is particularly dependent on beam size orthogonal to the traverse direction. Modeling allows some of the results encountered to be explained in terms of temperature distributions and cooling rates. Fiber coupling seems to provide a benefit if even thin-wall dimensions are required for applications such as rapid prototyping, while using the rectangular beam provides advantages for bulk material addition for applications such as repair and refurbishment of worn components.
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