Tensile properties of laser additive manufactured Inconel 718 using filler wire
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National Research Council Canada – Aerospace, Montreal, Quebec H3T 2B2, Canada
Mamoun Medraj Department of Mechanical Engineering, Concordia University, Montreal, Quebec H3G 1M8, Canada (Received 21 January 2014; accepted 20 June 2014)
A 5 kW continuous wave fiber laser welding system was used to deposit INCONELÒ alloy 718 (IN718) on service-exposed IN718 parent metal (PM) substrates using filler wire addition. The microstructure of the deposits was characterized in the fully heat treated condition. The service-exposed IN718 PM and the direct laser deposited (DLD) specimens were then evaluated through room temperature tensile testing. The yield and tensile strengths were well above the minimum values, as defined in the aerospace specifications AMS 5596K and 5663M. However, the ductility at room temperature of the DLD and DLD-PM samples was slightly lower than that specified in AMS 5596K and 5663M. The tensile fracture surfaces of the service-exposed IN718 PM, DLD, and DLD-PM specimens were analyzed using scanning electron microscopy (SEM), and the tensile failure mechanisms are discussed in detail, particularly for the important roles of the secondary particles (MC carbides) and intermetallics (platelet Ni3Nb-d and Laves phases).
I. INTRODUCTION
As an emerging and sustainable fabrication technology, laser additive manufacturing allows rapid introduction of new designs, shortening of the product implementation cycle, and manufacturing and/or repairing to the near-net shape of the aerospace components, such as aeroengine subassemblies fabricated from nickel-based superalloys.1–3 During laser additive manufacturing, both powder and wire have been used as feedstock, but the latter has lower cost, higher material efficiency (reduced waste), lower contaminant pick-up (higher quality), lower oxidation (fewer defects), and higher deposition rate (productivity).4–7 To date, the microstructure and mechanical properties of laser additive manufactured IN718 using conventional CO2 and Nd:YAG lasers have been extensively studied.1,2,5,8–12 The typical tensile properties obtained for the IN718 alloy are summarized in Table I, including the results for the conduction-mode condition generally used for direct laser deposition, as well as the mechanical performance obtained for keyhole-mode laser welding of butt joints. Zhao et al.8 evaluated the mechanical properties of laser deposited IN718 using gas-atomized and plasma rotating electrode processed (PREP) powders. The tensile properties of the deposit using PREP powders were superior to the wrought IN718 alloy, while the performance of the gas-atomized powder deposit was a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.199 2006
J. Mater. Res., Vol. 29, No. 17, Sep 14, 2014
http://journals.cambridge.org
Downloaded: 16 Mar 2015
inferior, which was attributed to the presence of gas porosity in the feedstock that rendered porosity and microcracks in the microstructure. In contrast, Blackwell9 reported that tensile failure in laser d
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