Effect of Post-heat Treatment on the Load-Dependent Wear Mechanisms of AISI D2 Tool Steel Manufactured by Laser Direct Energy Deposition

초록

The microstructure and wear behavior of AISI D2 cold work tool steel fabricated using a laser-based direct energy deposition (DED) process were investigated and compared with those of conventional Wrought AISI D2 steel. The effect of post-heat treatment on wear performance was also examined. Post-heat-treated DED samples exhibited a martensitic matrix embedded with needle-shaped secondary carbides, whereas the Wrought steel showed a martensitic matrix containing coarse primary carbides and globular secondary carbides. Among all three samples (as-built DED, heat-treated DED, heat-treated Wrought), the as-built DED specimen showed the highest wear loss and wear rate with increasing load, while the post-heat-treated DED specimen demonstrated the lowest values, indicating superior wear resistance. The lowest wear resistance of the as-built DED sample was primarily attributed to retained austenite and the absence of secondary carbides. In contrast, the fine martensitic structure and homogeneously distributed secondary carbides in the heat-treated DED sample significantly enhanced its wear resistance. The heat-treated Wrought sample exhibited reduced wear resistance due to the spalling of coarse primary carbides under localized stress. Debris analysis revealed that all samples formed oxide-based tribolayers due to frictional heat at high wear load. Notably, adhesive debris formation in the Wrought sample contributed to a noticeable reduction in the coefficient of friction with increasing load.

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