Laser cladding of Co-based alloy/TiC/CaF2 self-lubricating composite coatings on copper for continuous casting mold

Abstract

In this study, Co-based alloy/TiC/CaF2 self-lubricating composite coatings were successfully prepared on a Cr-Zr-Cu alloy for continuous casting mold by Nd:YAG laser cladding. The microstructure, phase structure and wear properties were investigated by means of scanning electron microscopy (SEM) incorporating energy dispersive X-ray (EDX) and X-ray diffraction (XRD), as well as dry sliding wear test against GCr15 steel at a temperature of 400°C. The results showed that the Co-based alloy/TiC/CaF2 self-lubricating composite coatings had a unique microstructure consisting of well-developed small fine spherical TiC and CaF2 particles uniformly dispersed in the γ-Co matrix. Average hardness of the Co-based alloy/20% TiC/10% CaF2 (vol.) self-lubricating composite coating was about twice times that of the pure Co-based alloy coating. It was found that the laser cladding Co-based alloy/TiC/CaF2 coatings on copper had good friction-reducing and antiwear abilities at temperature up to 400°C. The composite coating obviously decreased friction coefficient and wear rate as the volume fraction of CaF2 increased and TiC decreased. The laser cladding Co-based alloy/20% TiC/10% CaF2 (vol.) composite coating was characterized by mild adhesion wear and plastic deformation and relatively smooth wear surface could be observed.