ABSTRACT
Objective:To investigate the feasibility of improving the corrosion resistance of nickel-chromium alloys by the means of cryogenic treatment. Methods:16 disk samples were divided into 4 groups, including control group(C), cryotreat group(E1),tempering after cryotreat group(E2) and simulative porcelain sintering after cryotreat group(E3). All samples were subjected to electrochemical potentiodynamic polarization after immersed in the artificial saliva ISO/TR 10271:1993(E) pH 6.8 for 24 h at ambient temperature. The metallography of all groups were observed by SEM. Results:①Cryogenic treatment elevated the pitting corrosion potential and dropped the corrosion current of Ni-Cr alloys. Following simulative porcelain sintering,as well as tempering after cryotreat, decreased the corrosion current. But the corrosion potential of Ni-Cr alloys fell after cryotreat and following simulative porcelain sintering. Tempering after cryotreat did not affect the pitting corrosion potential. ②Much small secondary substance separated out and evenly distributed along the crystals of Ni-Cr alloys after cryotreat. Conclusion:Cryogenic treatment effectively improves the electrochemical corrosion resistance of Ni-Cr alloys, and tempering following cryotreat is unnecessary. It is not recommended to sintering porcelain after cryogenic treatment.