Effect of Laser Scanning Speed on the Tribological and Wear Resistance Properties of h-BN/TC4 Composite Coatings
摘要
To enhance the poor wear resistance of TC4 alloy surfaces, this study investigated the effects of laser scanning speed (10, 11, and 12 mm/s) on the microstructure and tribological properties of laser-cladded h-BN/TC4 coatings. Under a laser power of 1200 W, three crack-free coatings were successfully fabricated and characterized using SEM, EDS, and XRD, while their tribological behavior was evaluated by microhardness and high-temperature wear tests. As the scanning speed increased, the h-BN content in the coatings gradually rose, and its distribution changed from intergranular to a discrete pattern. The coating produced at 11 mm/s achieved the highest microhardness of 539.6 HV0.5, 1.54 times that of the substrate. At room temperature, the 10 mm/s coating showed the lowest wear rate (0.97 and 0.80 times those of the 11 mm/s and 12 mm/s coatings), mainly exhibiting abrasive and mild oxidative wear with slight fatigue wear. At 600 °C in air, the 12 mm/s coating demonstrated the best wear resistance (0.78 and 0.83 times those of the 10 mm/s and 11 mm/s coatings), attributed to synergistic lubrication from h-BN and the oxide film. Under 600 °C argon, the 10 mm/s coating displayed the lowest wear rate (0.99 and 0.66 times those of the 11 mm/s and 12 mm/s coatings). The absence of oxidation in argon shifted the dominant mechanism from oxide-film-assisted to one governed by plastic deformation and abrasive wear. Here, the combined effect of the h-BN transfer film and glaze-like tribolayer provided interfacial lubrication, effectively reducing asperity contact and surface tearing. Overall, the coating wear resistance results from the dynamic balance between oxide/transfer film protection and h-BN self-lubrication, with the argon atmosphere favoring the latter mechanism.
Graphical abstract