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

• Published in: Optics and laser technology Vol. 66; pp. 98 - 105
• Main Authors: Sun, G.F., Wang, K., Zhou, R., Tong, Z.P., Fang, X.Y.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2015
• Subjects: Annealing; Coatings; Friction; Laser direct metal deposition; Lasers; Mechanical properties; Microhardness; Microstructure; Residual stress; Wear; Mechanical properties; Annealing; Laser direct metal deposition
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2014.08.005

Laser deposited Co-285+WC coating was heat treated at 500°C (stress relief annealing) for 60min 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. •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.