Product Code: ICAL06_1001

Laser Cladding of Cu-NbC Nanocomposite Coatings
Authors:
Amelia Almeida, Instituto Superior Tecnico; Lisboa Portugal
Sonia Eugenio, Instituto Superior Tecnico; Lisboa Portugal
Teresa Marques, INETI-DMTP; Lisboa Portugal
Vanessa Livramento, INETI-DMTP; Lisboa Portugal
Jose Brito Correia, INETI-DMTP; Lisboa Portugal
Rui Vilar, Instituto Superior Tecnico; Lisboa Portugal
Presented at ICALEO 2006

Cu-matrix composites are interesting materials to be used as coatings in applications where efficient heat transfer and good wear resistance are simultaneously necessary, like mould repair, electric sliding contacts, high temperature seals, etc. In this work, Cu-NbC nanocomposite powder was synthesized in-situ by mechanical alloying from elemental mixtures of Cu, Nb and graphite powders. The composite powder was used to produce Cu-10% NbC coatings on a CK45 steel substrate by laser cladding. The coatings have an average thickness of 800 μm and present some porosity due to the oxidation of the powder and consequent incorporation of oxygen in the coating. Their microstructure was characterized by SEM, EDS, XRD and TEM analysis. It consists of very fine (submicron sized) NbC particles uniformly distributed in the Cu matrix. The coatings present an average microhardness of 200 HV. The wear behavior of the coatings was investigated through microscale wear tests performed under dry sliding conditions against a steel counterbody. The influence of load on the prevailing wear mechanisms was analyzed and related to the microstructure of the coatings. Wear is moderate at low loads, mainly by oxidation. At higher loads a transition to abrasive wear by hard particles resulting from the oxide layer occurs and the wear coefficient increases. However, the wear coefficients are relatively low (10 ^-13 m2/N) and wear remains in the moderate regime.