Fabrication, Microstructure and Wear Properties of High Carbon Tool Steel Coating Layer Manufactured by Laser Direct Energy Deposition

Recently, research on tool parts and materials for converting high-strength, lightweight materials into components is actively underway. High carbon tool steel (D2) coating layers were manufactured by using direct energy deposition (DED) process in this study. Post-heat treatment was applied to the as-built layers. The wear properties of DED high carbon tool steel layers were were examined with heat treatment. To compare microstructure and wear properties, conventional wrought D2 bulk material was also prepared and analyzed together. DED as-built samples were fabricated with the thickness of 8 mm and nearly defect free. The as-built layers represented columnar dendrite microstructure. Austenite matrix and eutectic structure were observed in the as-built D2 layer, and martensite matrix and secondary Cr-rich carbide were detected after heat treatment. The maximum tensile strengths of as-built and heat treated D2 layers were measured as 1016 MPa and 1794 MPa, respectively. Wear loss increased with wear load (20~40 N), and DED heat treated D2 layer represented lowest wear loss (highest wear resistance) compared to those of both DED as-built layer and wrought material. In connection with the microstructure of each material, the wear mechanism of DED high carbon tool steel layer was also discussed.