Laser clad Ni-base alloy added nano- and micron-size CeO2 composites

Micron-size Ni-base alloy (NBA) powders are mixed with both 1.5 wt% (%) micron-CeO2 (m-CeO2) and also 1.0-3.0% nano-CeO2 (n-CeO2) powders. These mixtures are coated on low carbon steel (Q235) by 2.0 kW CO2 laser cladding. The effects on microstructures, microhardness and wear resistance of the coating by the addition of m- and n-CeO2 powders to NBA (m- and n-CeO2/NBA) have been investigated. Addition to the primary phases of gamma-Ni, Cr23C6 and Ni3B of NBA coating, CeNi3 shows up both in m- and n-CeO2/NBA coatings and CeNi5 appears only in n-CeO2/NBA coating. Directional dendrite and coarse equiaxed dendrite are grown in m-CeO2/NBA coating from interface to central zone, whereas multi-oriented dendrite and fine equiaxed dendrite growth by addition of n-CeO2. The microhardness and wear resistance of coatings are greatly improved by CeO2 powder addition, and compared to the addition of 1.0% and 3.0%, 1.5% n-CeO2/NBA is the best. Hardness and wear resistance of the coating improves with decreasing CeO2 size from micron to nano. (C) 2007 Elsevier Ltd. All rights reserved.