In Situ Scanning Electron Microscopy Investigation of Failure Mechanisms in Multilayer Coatings

Area of Science:

• Materials Science
• Tribology
• Surface Engineering

Background:

• Optimizing tribological performance of multilayer coatings requires understanding their failure mechanisms.
• TiN/Ag multilayer coatings are promising for wear-resistant applications.

Purpose of the Study:

• To investigate the failure mechanisms and tribological performance of TiN/Ag multilayer coatings.
• To correlate coating structure, stacking sequence, and topmost layer with wear behavior and scratch resistance.

Main Methods:

• In situ scanning electron microscopy (SEM) tribotester for simultaneous friction monitoring and wear visualization.
• Ultrananoscratch testing for scratch resistance evaluation.
• Focused ion beam (FIB) cross-sectional analysis for post-test failure mechanism investigation.

Main Results:

• Soft-top (ST) structures with Ag as the topmost layer demonstrated superior damage resistance and wear stability over hard-top (HT) structures with TiN.
• In situ SEM revealed diverse wear behaviors including groove formation, delamination, and cracking.
• Failure mechanisms identified include shear deformation, interlayer cracking, and crack filling due to stress cycling.
• The ML10ST coating exhibited the highest wear resistance, attributed to the plastic deformation of the Ag layer for stress dissipation.

Conclusions:

• The stacking sequence and topmost layer significantly influence the tribological performance and failure modes of TiN/Ag multilayer coatings.
• Soft-top structures offer enhanced wear resistance and stability compared to hard-top structures.
• Understanding stress dissipation mechanisms is crucial for designing advanced, durable multilayer coatings.