COVERING WITH CARBON BLACK AND THERMAL TREATMENT BY A CO2 LASER SURFACES OF AISI 4340 STEEL

This work presents the evaluation of the use covering with carbon black to replace the graphite covering used in previous work, aiming to eliminate the grinding step to the process. The results of this treatment were characterized by optical microscopy, scanning electron and hardness. The micro hardness achieved was near to 760 HV (0.05), coefficient of friction of 0.2. Scanning electron microscopy showed that the extent of the treated area by laser reaches near to 90 mu m, and the thickness coating of carbon black is about to 2 mu m. The graphite can be substituted by carbon black, acting as coupling of the laser beam radiation, and as a solid lubricant, according to REIS (2009).