Effect of Laser Remelting on Tribological Performance of Ni-Cr-B-Si Coatings Deposited by Laser Metal Deposition

Abstract:

Ni-superalloys coatings deposited via laser metal deposition (LMD) have been known to perform well in increasing components lifespan and consequently reducing production and repair costs. Although most of these coatings already present good results in its hardness, and tribological behavior, some can be improved by post-deposition treatments, such as laser remelting. In this ambit, the present paper aims to evaluate the laser remelting posttreatment effects on the Ni-Cr-B-Si coating sliding tribological behavior. For this, two conditions were compared: Ni-Cr-B-Si coating as-deposited and Ni-Cr-B-Si coating as-deposited and remelted. The coating’s occurrence of superficial macro defects, their microhardness, and tribological performance in the pin-on-disk (ASTM G99) test were compared. Friction coefficient (load cell), volumetric loss (optical interferometry), Archard's wear coefficient and worn surfaces (SEM and EDS), were evaluated. Results show that the laser remelting posttreatment was effective in reducing cooling cracks, increasing hardness and reducing friction coefficient oscillation and volumetric loss average.

Key-words:
Ni-superalloys; Laser metal deposition; Laser remelting; Tribological performance; Cooling cracks