| Abstract |
| For surface hardening of a continuous casting mold component, a thermal spray coating of NiCrBSi (Metco-16C) and CoCrWC (Stellite-1) was performed followed by laser heat treatment of the coatings. To support selective modification of the thermal spray coating, a metallurgically determined surface temperature was maintained during the laser heat treatment, by real-time control of the laser power. In other words, nonhomogeneities in the macrosegregation of certain alloying elements, and voids in the as-sprayed state, could be improved. The main microstructural features of the Metco-16C coating laser-heat-treated at 1423 K were nanosized (100-150 nm) Cr5B3, M7C3, and M23C6 precipitates with a lamellar structure of Ni (FCC) and Ni3Si as the matrix phase. Those of the laser heat-treated Stellite- 1 coating at 1473 K were fine (30-250 nm) precipitates of WC, M7C3, and M23C6 based on a Co (FCC) matrix. The results show that laser heat treatment at 1423 K increased the hardness of the Mecto-16C coating to 1115 HV from the as-sprayed state (754 HV), while treatment at 1473 K increased the hardness of the Stellite-1 coating from 680 HV to 860 HV.
(Received December 6, 2019; Accepted February 4, 2020) |
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| Key Words |
| thermal spray coating, laser heat treatment, carbides, borides |
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