Microstructural Evolution and Mechanical Properties of Direct Metal Laser-Sintered (DMLS) CoCrMo After Heat Treatment
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Microstructural Evolution and Mechanical Properties of Direct Metal Laser-Sintered (DMLS) CoCrMo After Heat Treatment KAUSTUBH KRISHNA BAWANE, DHEEPA SRINIVASAN, and DIPANKAR BANERJEE Microstructures and tensile properties of Direct Metal Laser-Sintered (DMLS) CoCrMo were investigated in the as-printed condition and after heat treatment. A dense (> 99.5 pct) as-printed DMLS CoCrMo was obtained in the as-printed condition eliminating the need for any hot isostatic pressing. Solution heat treatment carried out at 1150 C revealed complete recrystallization resulting in an equiaxed grain structure with an average grain size of 40 lm. The microstructure after solution heat treatment and aging at 980 C revealed inter and intragranular precipitations, enriched in Mo and Si. Solution treatment resulted in the decrease of the room-temperature tensile strength from 1378 MPa (as-printed) to 1114 MPa, which was attributed to the increasing grain size from 0.6 to 1 lm (column width) to ~ 40 lm (grain size). The decrease in yield strength was accompanied by the increasing ductility from 5.7 to 15 pct. An enhancement in ductility to nearly 25 pct was observed in tensile tests at 925 C. This paper comprises a detailed microstructural evaluation of DMLS CoCrMo alloy to determine its suitability for high-temperature structural applications involving repair and refurbishment of components, including an evaluation of microstructural and tensile properties after welding the DMLS CoCrMo to cast FSX414. https://doi.org/10.1007/s11661-018-4771-4 The Minerals, Metals & Materials Society and ASM International 2018
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INTRODUCTION
ADDITIVE manufacturing via the direct metal laser-sintered (DMLS) process is gaining popularity in various sectors of structural engineering components as an economic approach to fabricating very expensive hardware made of high-temperature alloys. The key advantage of using the 3D printing approach is in its ability to compress the design cycle and reduce part development time by over 70 to 80 pct, compared with the current processes.[1] In addition, additive manufacturing paves the way for new engineering capability to optimize part and system designs in a way that cannot be achieved with the traditional manufacturing processes. Thus, the reduced part counts, minimized inventory, increases in the first pass yield, the improved design of parts, systems, and shapes once thought impossible to
KAUSTUBH KRISHNA BAWANE and DIPANKAR BANERJEE are with the Department of Materials Engineering, Indian Institute of Science, Bangalore, India. Contact e-mail: [email protected] DHEEPA SRINIVASAN is with GE Power, GE India Industrial Pvt. Ltd., Bangalore, India. Contact e-mail: [email protected] Manuscript submitted March 26, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
make, thereby enabling realization of products that are lighter, stronger, and more efficient, are all potential revolutionary advantages in design to manufacturing stages.[1–9] As a consequence, there has been extensive research on the DM
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