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<p>In this work, a 3D slab is fabricated through CMT + GMAW-based wire arc additive manufacturing by consuming ER70S-6 filler wire. The characteristics of the as-printed microstructure along with the mechanical properties (including tensile properties and microhardness) are studied. The as-printed microstructure is composed of polygonal ferrite and pearlite. The average tensile strength along the vertical direction appears approximately same as the horizontal direction. A similar observation is made in regard to the elongation at break. However, the tensile strength and elongation at break tend to vary location-wise. As compared to the bottom region (near the substrate), grain growth is witnessed at the top region of the slab. A higher tensile strength is obtained for the horizontal tensile specimen extracted from the bottom region of the slab than for the specimen extracted from the top region. The locational variation in the fracture strain appears more prominent in comparison with the tensile strength. Therefore, in the present work, the WAAMed ER70S-6 slab corresponds to an approximate isotropic tensile strength but shows anisotropy in the ductility when subjected to the tensile loading perpendicular to the build direction. The top region corresponds to a lower microhardness value than the bottom region of the slab. This is because the bottom region corresponds to a higher value of the dislocation density and lattice strain but a lower crystallite size. In the as-printed condition, the average tensile strength (UTS) of ~ 515&#xa0;MPa is obtained along the horizontal direction while the vertical direction exhibits ~ 518&#xa0;MPa. The as-printed specimen corresponds to a lower microhardness value (~203 HV<sub>0.5</sub>) than the post-heat-treated (900&#xa0;°C/1&#xa0;h and 4&#xa0;h + water quench) counterparts. The improved microhardness after the hardening treatment is due to the transformation of austenite to martensite, taking place during the rapid quenching process. During the hardening treatment, the 4-h holding duration causes a reduction in the microhardness value (~240 HV<sub>0.5</sub>) than the microhardness value obtained for the 1&#xa0;h holding (~287 HV<sub>0.5</sub>). Prolonged holding duration changes the martensitic morphology from acicular to lathy-type associated with the grain growth. This declines the microhardness value. The complicated thermal interaction phenomena of the WAAM process are also studied. This work introduces the concept of the ‘critical built height.’ A unified attempt is also made to fabricate a semi-closed impeller (also called as ‘WAAMpeller’) through the ER70S-6 wire arc deposition. Detailed procedural steps for the said ‘WAAMpeller’ fabrication followed by post-machining are reported.</p>

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Additive Manufacturing through ER70S-6 Wire Arc Deposition: Aspects of Built Microstructure and Mechanical Properties with an Attempt Toward Fabrication of a Semi-Closed Impeller

  • 期刊论文

  • 发表日期：

    2025年11月23日

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  • Arvind Kumar Jha,
  • Sameer Anand,
  • Nimai Haldar,
  • Sudipta Swain,
  • Parth Patel,
  • Saurav Datta,
  • Swapan Kumar Karak

摘要

In this work, a 3D slab is fabricated through CMT + GMAW-based wire arc additive manufacturing by consuming ER70S-6 filler wire. The characteristics of the as-printed microstructure along with the mechanical properties (including tensile properties and microhardness) are studied. The as-printed microstructure is composed of polygonal ferrite and pearlite. The average tensile strength along the vertical direction appears approximately same as the horizontal direction. A similar observation is made in regard to the elongation at break. However, the tensile strength and elongation at break tend to vary location-wise. As compared to the bottom region (near the substrate), grain growth is witnessed at the top region of the slab. A higher tensile strength is obtained for the horizontal tensile specimen extracted from the bottom region of the slab than for the specimen extracted from the top region. The locational variation in the fracture strain appears more prominent in comparison with the tensile strength. Therefore, in the present work, the WAAMed ER70S-6 slab corresponds to an approximate isotropic tensile strength but shows anisotropy in the ductility when subjected to the tensile loading perpendicular to the build direction. The top region corresponds to a lower microhardness value than the bottom region of the slab. This is because the bottom region corresponds to a higher value of the dislocation density and lattice strain but a lower crystallite size. In the as-printed condition, the average tensile strength (UTS) of ~ 515 MPa is obtained along the horizontal direction while the vertical direction exhibits ~ 518 MPa. The as-printed specimen corresponds to a lower microhardness value (~203 HV0.5) than the post-heat-treated (900 °C/1 h and 4 h + water quench) counterparts. The improved microhardness after the hardening treatment is due to the transformation of austenite to martensite, taking place during the rapid quenching process. During the hardening treatment, the 4-h holding duration causes a reduction in the microhardness value (~240 HV0.5) than the microhardness value obtained for the 1 h holding (~287 HV0.5). Prolonged holding duration changes the martensitic morphology from acicular to lathy-type associated with the grain growth. This declines the microhardness value. The complicated thermal interaction phenomena of the WAAM process are also studied. This work introduces the concept of the ‘critical built height.’ A unified attempt is also made to fabricate a semi-closed impeller (also called as ‘WAAMpeller’) through the ER70S-6 wire arc deposition. Detailed procedural steps for the said ‘WAAMpeller’ fabrication followed by post-machining are reported.