Analysis of Anti-Wear Protective Coating on a Component from a Data Recording System

Thin coatings with specifically designed properties are widely used in industry, but in addition the design of new coatings is of prime importance in some sectors. The example presented here is a chromium oxide anti-wear protective coating on a Co component from a data recording system. Scratch testing was employed to investigate the abrasive wear resistance of the coating and Auger electron spectroscopy was used to characterize the failure mode. 10mN to 50mN loads were applied to the scratch indenter, as this range of loads covers plastic deformation, cracking, delamination and failure of coating.

Scratched 40nm thick Cr2O3 coating with increasing scratch indenter force (each SEM image is 6µm×7.5µm)

40nm thick Cr2O3 coating on Co substrate with 30mN scratch force. SEM image (left) and AES Co image (middle), Cr image (right) (each image is 3µm×4µm)

The images above show typical Auger images after the coating has been partly removed. The images show that coating failure and removal under 30mN scratch force revealing the Co substrate.

The Auger electron investigation showed that the coating survived a considerable degree of plastic deformation before failure began to occur showing the usefulness of the technique as a tool for investigating coating failure. From this analysis, a better understanding of coating behaviour can be gained leading to the development of better anti-abrasive wear nano-scale coatings. From the results it is also possible to examine coating/substrate adhesion and mechanisms of failure of coatings under severe abrasive conditions. The measured wear rate of the Cr2O3 coating, using AES depth profiling, is around 5.6×10-21 m3/N·m using a real data system during this investigation. Further study aimed at improving these coatings and increasing their wear resistance is in progress for our customers.

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