Erosion mechanism of the boron-doped diamond films of different thicknesses

Chemical vapor deposition (CVD) diamond film has extensively applied as the protective coating under hostile and abrasive conditions, the erosion mechanism of which is significantly influenced by the composition and thickness of the film. This paper describes an erosion study, which examines the effects of the film thickness on the erosive wear behavior of the boron-doped diamond (BDD) films deposited on the SiC substrates by the hot filament CVD (HFCVD) method, with the undoped ones as comparisons. A laboratory designed air-sand erosion rig is used to conduct the erosion tests, with the velocities in the range of 100-140 m/s and 90° nominal impact angle. The erodents are silica sands with an average diameter of 180 μm. The diamond films are examined both pre- and post-test by the field emission scanning electron microscopy (FESEM) in order to determine the erosion mechanisms of the diamond films. Firstly, it is observed that the higher residual compressive stress and critical tensile strength can slow down the formation of the ring cracks. Moreover, the 12 μm diamond film has the highest steady-state erosion rate because the depth of the maximum shear stress is much close to the film-substrate interface. Furthermore, the complicated effects of the film thickness on the film lives of both the BDD and undoped diamond films are also further studied, as well as the velocity exponents of the different diamond films. The research results in the present study are conductive to the widespread applications of BDD films on the erosion resistant components.