Laser-Directed Energy Deposition of AISI H13 on copper‑beryllium alloy substrates with Ni buffer

Steel/copper alloy multi-material structures fabricated via metal additive manufacturing hold significant promise for applications such as molding and tooling. However, the formation of a steel/copper alloy interface is highly susceptible to solidification cracking. In this study, AISI H13 cladding was deposited on copper‑beryllium alloy substrates using Laser-Directed Energy Deposition. A commercial pure Ni buffer was employed to mitigate cracking, as evidenced by the crack-free Ni-buffered specimens. The effectiveness of Ni in suppressing cracking can be attributed to two key factors: (i) establishing a chemical composition gradient from copper‑beryllium to H13, thereby minimizing solidification cracking susceptibility across the entire composition range, and (ii) reducing residual stress caused by the mismatch in the coefficient of thermal expansion between H13 and copper‑beryllium. The solidification cracking susceptibility in the Fe-Cu-Ni ternary system was qualitatively assessed by calculating key solidification characteristic values, including the solidification temperature range and the amount of terminal liquid, using Scheil's model. Easton's solidification cracking model was validated as a reliable tool for quantitatively evaluating cracking susceptibility in the Fe-Cu-Ni system. Both approaches indicated that introducing a Ni buffer creates a path with low cracking susceptibility. The as-deposited H13 exhibited high microhardness (580–690 HV) compared to the copper‑beryllium alloy (400 HV), significantly enhancing the load-bearing capability. While softer materials such as in-situ tempered martensite, Ni buffer, and heat-affected zone negatively impact the load-bearing capacity, this can be restored by increasing the number of H13 layers. Based on the typical stress levels in injection molding dies, a 3 to 5 mm thick H13 cladding is deemed sufficient to protect mold surfaces made of copper alloys.