Effect of interlayer temperature on the microstructure and mechanical properties of new Co-Free maraging steel fabricated by arc-based directed energy deposition

Abstract

To establish process standards for arc-based directed energy deposition (DED-Arc) of the self-developed, low-cost Co-free maraging steel welding wire, the effect of different interlayer temperatures (50 °C and 350 °C) on the microstructure and mechanical properties of thin-walled components was studied. At an interlayer temperature of 50 °C, the average grain size of the specimens reached 14.06 μm, with high-angle grain boundaries (HAGBs) accounting for 49.5 %. The austenite content was 6.8 %, and the geometrically necessary dislocation (GND) density was 1.99 × 10¹⁴ m⁻². When the interlayer temperature was increased to 350 °C, the average grain size increased significantly to 31.33 μm, accompanied by a decrease in the proportion of HAGBs to 45.5 %. Additionally, the austenite content rose to 11.8 %, while the GND density decreased to 1.71 × 10¹⁴ m⁻². For specimens tested at an interlayer temperature of 50 °C, the tensile strength in the X-direction reached 1211.8 MPa with an elongation of 11.7 %, while in the Z-direction, it was 1186.6 MPa with an elongation of 8.7 %. However, increasing the interlayer temperature to 350 °C resulted in a decrease in tensile strength to 996.8 MPa and an increase in elongation to 23.4 % for X-direction specimens. Similarly, in the Z-direction, the tensile strength decreased to 969.1 MPa with an elongation of 22.2 %. Notably, increasing the interlayer temperature from 50 °C to 350 °C significantly enhanced impact toughness by adding up to 42.5 J/cm² for X-direction specimens and by 32.4 J/cm² for Z-direction specimens. The microhardness values of the deposited components were 352.4 HV and 300.3 HV at interlayer temperatures of 50 °C and 350 °C, respectively.