Effect of annealing on microstructure and mechanical properties of laser deposited Co-285+WC coatings

• FWHM of presented peaks were decreased by annealing.
• Residual stress changed from tensile to compressive stress.
• Microhardness decreased by 39% by annealing.
• Relative wear resistance was improved by 6.8 times by annealing.
• Good toughness, formation and good adhersion of oxide films improved wear resistance.

Laser deposited Co-285+WC coating was heat treated at 500 °C (stress relief annealing) for 60 min and cooled to room temperature in a furnace. Optical, scanning microscopy and X-ray diffractometer were used to investigate the microstructure and phases in the coating. An X-ray stress analyzer was used to study the effect of heat treatment on the residual stress in the coating. A microhardness tester and wear tester were used to test the microhardness distribution and friction and wear behavior. A lot of precipitates formed in the annealed Co-285+WC coating. Residual stress and FWHM (full width at half-maximum) of the coating were decreased by annealing. Residual stress values and microhardness decreased by 22–88% and 39%, respectively. Friction coefficient seldom changed by annealing, but circulation of oxide films was brought forward. Relative wear resistance of the annealed Co-285+WC coating was 6.8 times that of the as-deposited coating. Mechanism of the effect of annealing on microstructure, FWHM, residual stress and wear properties were discussed.