Abstract
Tremendous discrepancies in the positive enthalpy of mixing and the coefficient of thermal expansion emerge between the copper alloy and the gray cast iron, accounting for numerous pores and cracks in the interfacial region during the metallurgical bonding process. To enhance the interfacial bonding properties of these two refractory materials, laser-directed energy deposition was applied to fabricate the CuSn15 alloy on the HT250 substrate; meanwhile, Inconel 718 alloy, acting as the interlayer, was added to their bonding region. Firstly, the effect of the deposition process on deposition layer quality was investigated, and then the effects of Inconel 718 addition on the interfacial morphology, element distribution, phase composition, bonding strength, microhardness were studied. The results showed that a substrate (HT250) without cracks and a deposition layer (CuSn15) free from pores could be obtained via parameter optimization combined with preheating and slow cooling processes. Adding the Inconel 718 interlayer eliminated the interfacial pores and cracks, facilitated interfacial element (Cu, Fe, Ni) diffusion, and enhanced interfacial bonding strength. The interface between HT250 and CuSn15 mainly contained the FeSn2 phase, while the interfaces of the CuSn15-Inconel 718 and the Inconel 718-HT250 were mainly composed of the Ni3Sn4, Cr5Si3, FeSi2, Cr7C3. The microhardness and fracture morphology of the interfacial region in the samples with and without the interlayer were also studied. Finally, CuSn15 was also successfully deposited on the surface of the HT250 impeller with large size and complex structure, which was applied in the root blower.
Highlights
Gray cast iron finds extensive use in the manufacture of molds, cams, machine tool beds, impellers, etc., in various fields requiring large equipment, on account of its excellent machinability, castability, thermal conductivity, and shock absorption, as well as its cost effectiveness [1,2]
Some challenges are presented in the repair of gray cast iron components via Laser-directed energy deposition (LDED), such as the elimination of the cracks and pores that tend to form at the bonding interface and the heat-affected zone
Ocelík et al [20] deposited thick Co-based alloy via LDED on gray cast iron, and plenty of pores and cracks developed. These defects have negative impacts on interfacial bonding strength, so some researchers have endeavored to adopt measures such as laser remelting [17,21], parameter optimization [22], preheating [23], etc., to reduce or eliminate the defects generated in the interface region during the LDED process
Summary
Gray cast iron finds extensive use in the manufacture of molds, cams, machine tool beds, impellers, etc., in various fields requiring large equipment, on account of its excellent machinability, castability, thermal conductivity, and shock absorption, as well as its cost effectiveness [1,2]. LDED has been identified as an effective method for repairing and strengthening the surface of gray cast iron through the deposition of copper- and nickel-based alloy, both of which possess superior corrosion resistance and strength.
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