Preparation Technique Of Carbon-Based Coatings On The Magnesium Alloy And Mirco-Structure Study

In this paper, influence rule of coatings/substrate bond strength resulted from the pit with nanophase dimension caused by the ion bombardment, structure characteristic of dilution zone at the coating/substrate interface, and the structure characteristic of gradient transition, and frictional wear of carbon-based top layer were all analyzed by the SEM, TEM, XPS, a Vickers microhardness tester, a scratch tester and a ball-on-disk tester.The results show that, the pit with nanophase dimension caused by the ion bombardment has strong influence on the coating/substrate bond strength. High bias voltage can clean out oxide skin drastically, however, the "flocculent" tectorium will weaken the coating/substrate bond strength under the over bias voltage. Also low bias voltage can not remove the oxide skin effectively. The best ion bombardment technology was -300V/20min. Selecting Zr target with the same crystal structure and Cr target with the different crystal compared with Mg, election principle of prime layer when depositing carbon-based antifriction coatings on light metals was also discussed. The result disclosures they all form dilution zone at the coating/substrate interface, and have equal coating/substrate bond strength. Surface pattern of the carbon-based antifriction and structure characteristic of gradient transition were changed under different bias voltage. Pattern with banded groove and visible grain was presented at low bias voltage. With the bias voltage increasing, banded groove vanished and smoothness intensified obviously; finally, large grain bulged, small grain coagulated, and the banded groove appeared again with the bias voltage increased sequentially; Top layer all presented non crystalline structure under different bias voltage. XPS shows that the main component was amorphous carbon, Cr₂O₃ and Cr elementary, also no chemical compound composed by Cr and C. With the bias voltage increasing, the thickness of coatings decreased, the compound hardness and friction coefficient presented decreased first then increased. The friction coefficient with 0.06～0.1 was lowest at the -35 bias voltage.