Production of composite coating of hard chrome - nano alumina by electroplating from the bath of hexa valence chrome and the study of the hardness and abrasive properties

This research paper aimed at study of the effect of two critical parameters on the electroplating of nano composite coatings that are, the weight percent of alumina nanoparticles dispersed on the electroplating bath and the density of electrical current. The amount of distributed nanoparticles influences the resistance to abrasion, coating microstructure and adhesion to substrate The hard chrome coating and nano composite coating of chrome – alumina by using of direct current and electroplating bath of hexavlence chrome. optical microscope images, SEM/EDS, XRD, micro vikers hardness test and the abrasion test of pin on the disc. The results of these examinations showed that the maximum amount of nano alumina, distributes into the nano composite coatings when electroplating conditions set on 25 grams of nano alumina per liter of bath, and the current density was 50 amps on square decimeters .SEM images were resolved the presence of nano-alumina particles that distributed into volume of coated layer XRD reveals that the size of grain in coated layer with nano-alumina was reduced noticeably and with increasing the volume density of nano particle in coated layer the grain size of coating structure reduces. Comparison between hard chrome coating and the nano-composite coating of chrome-alumina showed that the coating containing of nano-alumina particles is 46% harder and enjoys 179 times more abrasion resistance as compared to hard chrome.