Improved crack resistance and toughness of laser-clad H13 steel coatings enabled by CoCrFeNi transition layer

Abstract

Current research on directed energy deposition (DED) repair predominantly focuses on enhancing surface properties while often neglecting quench-induced embrittlement in thermally sensitive materials like H13 steel, which can lead to premature failure under service loads. To address this, a ductile CoCrFeNi alloy transition layer was introduced between a TiC-reinforced wear-resistant coating and the H13 substrate, forming a "hard-soft-hard-soft" laminated structure that eliminates the need for post-repair heat treatment. This approach alleviates stress concentration in the brittle heat-affected zone (HAZ) through modulus-gradient-driven stress redistribution and crack energy dissipation via the plasticity of the transition layer. Experimental results demonstrate an 80 % reduction in crack density and a 22 % increase in impact resistance. The synergy between the stress-buffering transition layer and the energy-dissipating protective coating establishes a dual-protection mechanism, safeguarding the substrate from catastrophic failure. This work redefines the paradigm of laser-based repair by simultaneously mitigating embrittlement and enhancing surface hardening, offering generalizable for laser repair of quench-prone materials (e.g., tool steels, martensitic stainless steels) in heavy-duty machinery and aerospace applications.