Improved Mechanical Properties of Al₂O₃ Ceramics by Sputtered TiN Coatings

Abstract

In this study, TiN thin lms have been prepared as the coating layers on Al 2 O 3 ceramic substrates to enhance the mechanical properties of Al 2 O 3 ceramics. TiN lms with various thicknesses of 0.5 and 1 μm were deposited by DC sputtering at room temperature. The TiN lm prepared on the Al 2 O 3 substrate has a columnar structure without large bumps or steps formed on the lm s surface. Without the TiN coating, the average friction coef cient of the Al 2 O 3 substrate was 0.51. As 0.5-and 1-μm-thick TiN lms were coated on Al 2 O 3 substrates, the average friction coef cients of these two samples reduced to 0.36 and 0.32, respectively, revealing the tribological characteristics of Al 2 O 3 ceramic was enhanced with the TiN coating. Additionally, the 1-μm-thick TiN/Al 2 O 3 sample possesses a slightly higher attrition resistance than that of the 0.5-μm-thick TiN/Al 2 O 3 sample, and this can be also con rmed by performing the elemental mapping method on the wear-treated samples. From the adhesion performances, we observed no critical load of L C2 appeared in these two samples during the scratch test, while the critical load of L C1 values were 11 and 9 N for 0.5-μm-thick TiN/Al 2 O 3 and 1-μm-thick TiN/Al 2 O 3 , respectively. Due to the increment of TiN thickness, the internal stress formed in the lm would increase. This is the reason why the 1-μm-thick TiN/Al 2 O 3 sample has a lower critical load of L C1 . Obviously, the 0.5-μm-thick TiN lm coated on the Al 2 O 3 substrate has a better adhesion characteristic. According to these results, the sputtered TiN coating is indeed useful for improving the mechanical properties of Al 2 O 3 ceramics, in particular for the 0.5-μm-thick TiN coating. [