激光辅助冷喷涂增材再制造 CuCrZr 结晶器研究

CuCrZr alloy, owing to its excellent comprehensive performance, has become an ideal material for manufacturing continuous casting mold copper plates. However, under harsh service conditions, mold copper plates encounter failures such as thermal fatigue cracks, creep deformation, surface wear/corrosion and cooling water erosion, etc. Existing surface repair and strengthening technologies still have certain limitations. Therefore, it is necessary to develop a new additive re-manufacturing technology for failed CuCrZr mold copper plates. Laser-assisted cold spray (LACS) is an emerging laser hybrid manufacturing technology that offers high deposition efficiency, minimal thermal damage to the substrate, and good interface bonding. It shows great potential for surface strengthening and additive manufacturing/re-manufacturing of metal components. In this study, LACS is employed to achieve additive re-manufacturing for failed CuCrZr substrates. The influence of different laser powers on the microstructure of the deposited layer is systematically discussed. Subsequent heat treatment of the re-manufactured layer is carried out considering actual service conditions, and the thermal conductivity and interface bonding strength of the re-manufactured layer are analyzed in depth. The results show that the introduction of laser irradiation significantly improves the bonding between the additive re-manufactured layer and the CuCrZr alloy substrate. Without laser irradiation assistance, obvious gaps exist at the interface between the deposited layer and the substrate. As the laser power increases, the gaps due to poor bonding at the interface are markedly reduced. At 1 500 W laser irradiation, the bonding interface between the deposited layer and the substrate is very tight. However, at 2 000 W laser irradiation, some pores appear at the bonding interface. The introduction of laser irradiation also helps to improve inter-particle bonding with the deposited layer. The porosity of the deposited layer without laser irradiation and with 1 000, 1 500 and 2 000 W laser irradiation are 6.27%, 3.52%, 0.43% and 0.56%, respectively. Wihout laser irradiation, the additive re-manufactured CuCrZr alloy layer contains a large number of larger-sized pores. As the laser power increases, the number of pores decreases and the deposited layer becomes denser. The average microhardness values of the deposited layer under 1 000, 1 500 and 2 000 W laser irradiation are 153.482, 167.714, 170.067 and 168.789 HV0.2, respectively. Laser irradiation intensifies the plastic deformation of the deposited particles, inducing a work-hardening effect and thus higher hardness. XRD results show that the samples with laser irradiation and subsequent heat treatment maintain the same copper solid-solution phase as the sample without laser assistance, with no other imputity phase such as copper oxides detected. Post heat-treatment results reveal that the thermal conductivity of the 2 mm re-manufactured layer, the 1 mm re-manufacturing layer+1 mm substrate, the 2 mm substrate are 305.44, 315.92 and 334.2 W/(m·K), respectively. The thermal conductivity of the LACS-CuCrZr re-manufactured layer is close to that of the cast CuCrZr substrate, which is attributed to the dense microstructure of the LACS-CuCrZr re-manufactured layer. The interface bonding strength between the LACS-CuCrZr re-manufactured layer and the CuCrZr crystallizer substrate before and after heat treatment is 96.39 and 121.43 MPa, respectively. Due to the synchronous coupling laser heating, the plastic deformation at the material at the interface between the re-manufactured layer and the substrate is enhanced, resulting in a higher bonding strength. Moreover, the subsequent heat treatment further improves the interface bonding. The fracture morphology is characterized by pits formed by subsequent particle impact within the re-manufactured layer. The failure location lies within the coating, and the failure mode is typical cohesive failure. The bonding strength at the interface between the re-manufactured layer and the substrate is greater than that within the re-manufactured layer. The research results demonstrate that the additive re-manufactured CuCrZr alloy layer prepared at a laser power of 1 500 W exhibits excellent overall forming quality and outstanding comprehensive performance: porosity of 0.43%, microhardness of 170.067 HV0.2, thermal conductivity of 334.2 W/(m·K), and interface bonding strength of 121.43 MPa. This work preliminarily verifies that LACS technology can serve as a new method for surface strengthening and additive re-manufacturing of crystallizer copper plates, providing a theoretical basis and technical support for its engineering application.