Simulation of erosive wear of CVD boron carbide coatings by static and repetitive nanoindentation

Bose, K. and Wood, R.J.K. (2001) Simulation of erosive wear of CVD boron carbide coatings by static and repetitive nanoindentation. 2nd World Tribology Congress, Vienna, Austria. 31 Aug 2001. 4 pp .

Abstract

This paper reports on initial work attempting to reproduce the erosive mechanisms found to operate under high-energy sand impingement on CVD boron carbide coatings. Static Hertzian tests were conducted using spherically capped cone indenters, 90° cone angle, of radii 20 and 40 µm. The calculated contact stresses generated were comparable with those predicted by dynamic Hertzian theory for 235 µm angular sand particles impacting between 65-270m/s and at 90°. The load varied between 1-7.5N and the depth of penetration between 1-5µm. The calculated depth of maximum shear stressis between 4-7µm, i.e. within the coating thickness. Discontinuities (Pop-in’s) are observed at loads over 2N during loading across several indentations on the surface. Microscopic examination of the indented coating surface revealed little surface damage, suggesting the discontinuities observed are predominantly a result of sub-surface damage. For repetitive indentation, at a single location, these discontinuities are magnified 3-5 times in depth with those compared to the static indentation tests. As the load is increased, the time of apparent failure shows a steady decrease. However, no widespread surface failure is observed even from these tests, suggesting the absence of local surface damage phenomena in the coating during multiple repetitive impacts.

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Contributors

Author: R.J.K. Wood

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