Effect of friction cycles on wear particle generation of carbon nitride coating against a spherical diamond

The in-situ observations of wear particle generation of carbon nitride coat ing on silicon repeatedly sliding against a spherical diamond have been stu died in terms of the critical friction cycles and normal loads. An environm ental scanning electron microscope (E-SEM), in which a pin-on-disk tribotes ter was installed, has in-situ provided direct evidence of when and how the wear particle generation do occur during the repeated sliding of carbon ni tride coating against a spherical diamond. The in-situ observations of non- conductive carbon nitride coating are therefore available free from surface charging with controllable relative humidity. The repeated sliding tests a t a sliding speed of 50 mu m/s have been carried out with the purpose of ob serving the 'No wear particle generation' region when varying normal load f rom 10 to 250 mN. It appears that until 20 friction cycles, the maximum Her tzian contact pressure P-max for 'No wear particle generation' can be impro ved from 1.39 Y to 1.53 Y if silicon is coated by carbon nitride with a thi ckness of 10 nm, where Y is defined as the yield strength of silicon. The a pplicable enlargement of the 'No wear particle generation' region of carbon nitride coating has therefore been comparatively discussed with the silico n substrate from the view points of the friction coefficient and the specif ic wear rate. The mode transition maps have also been summarized for the re peated sliding of carbon nitride coating in terms of 'No wear particle gene ration', 'Wear particle generation by microcutting' and 'Wear particle gene ration by microcutting and microfracturing' three typical modes. (C) 2000 E lsevier Science Ltd. All rights reserved.