The frictional resistance and machining quality when cutting carbon fiber\nreinforced plastics (CFRP) laminates are associated with tribological behavior\nof tool materials. In the present study, the tribological properties of three\ntypes of monolayer microcrystalline diamond (MCD) coatings, nanocrystalline\ndiamond (NCD) coatings and dual-layer MCD/NCD coatings sliding\nagainst CFRP are investigated under dry lubricated conditions using the rotational\nfriction tester. The coefficients of friction (COF), wear rate and worn\nsurfaces of the contacted surfaces are analyzed for the MCD-CFRP,\nNCD-CFRP and MCD/NCD-CFRP contacting pairs. The results show that\ncompared with the monolayer MCD and NCD, the bilayer of MCD/NCD\ncoating displays the lowest COF with the value of ~0.13, it is 42% and 55% of\nthe values for MCD and NCD coatings. Due to the rough surfaces of MCD,\nthe wear debris of CFRP on MCD samples exhibits the plowing effect. While\nfor the NCD and MCD/NCD samples, the wear fragments display the planar\nshapes. The wear rate of CFRP against MCD is more than twice that of CFRP\nagainst NCD, due to the excellent loading capacity. While the wear rate of\nCFRP against MCD/NCD is about twice than that of CFRP-NCD pairs. The\nbilayer of MCD/NCD combines the excellent advantages of high hardness of\nMCD and the smooth surface of NCD. It shows the broad application potential\nfor the bilayer coatings.
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