Laser Powder Bed Fusion of Inconel 718 Tools for Cold Deep Drawing Applications: Optimization of Printing and Post-Processing Parameters

Abstract

Inconel 718 (IN 718) powder is used for a laser powder bed fusion (LPBF) printer, but the mechanical properties of the as-built object are not suited to cold deep drawing applications. This study uses the Taguchi method to design experimental groups to determine the effect of various factors on the mechanical properties of as-built objects produced using an LPBF printer. The optimal printing parameters are defined using the result for the factor response to produce an as-built object with the greatest ultimate tensile strength (UTS), and this is used to produce a specimen for post-processing, including heat treatment (HT) and surface finishing. The HT parameter value that gives the maximum UTS is the optimal HT parameter. The optimal printing and HT parameter values are used to manufacture a die and a punch to verify the suitability of the manufactured tool for deep drawing applications. The experimental results show that the greatest UTS is 1091.33 MPa. The optimal printing parameters include a laser power of 190 W, a scanning speed of 600 mm/s, a hatch space of 0.105 mm and a layer thickness of 40 μm, which give a UTS of 1122.88 MPa. The UTS for the post-processed specimen increases to 1511.9 MPa. The optimal parameter values for HT are heating to 720 °C and maintaining this temperature for 8 h, decreasing the temperature to 620 °C and maintaining this temperature for 8 h, and cooling to room temperature in the furnace. Surface finishing increases the hardness to HRC 55. Tools, including a punch and a die, are manufactured using these optimized parameter values. The deep drawing experiment demonstrates that the manufactured tools that are produced using these values form a round cup of Aluminum alloy 6061. The parameter values that are defined can be used to manufacture IN 718 tools with a UTS of more than 1500 MPa and a hardness of more than 50 HRC, so these tools are suited to cold deep drawing specifications.

Recent Progress in Additive Manufacturing of Alloys and Composites

“…Additionally, Jiang et al [ 10 ] outlined an optimal process route for the preparation of Inconel 718 tools intended for cold, deep drawing applications. Utilizing Inconel 718 powder as the raw material, these authors optimized parameters for both Laser Powder Bed Fusion (L-PBF) and double annealing (DA), followed by surface finishing techniques.…”

Surface Roughness of Interior Fine Flow Channels in Selective Laser Melted Ti-6Al-4V Alloy Components

“…However, few studies have been conducted to enhance the internal surface texture of TC4 alloy embedded flow channels in lightweight space components via SLM. For open surfaces, the post-printing machining processes, such as milling and burnishing, can be used to enhance the dimensional accuracy and surface quality of SLM parts [ 43 , 44 ]. The conformal cooling channels [ 45 , 46 , 47 ] represent a valuable application of SLM as they are critical in reducing cooling times and residual stresses in molded plastic parts.…”