Development and growth time optimization of boron-doped micro-crystalline, undoped micro-crystalline and undoped nano-crystalline composite diamond film

Abstract

Based on a well-designed growth procedure, a tri-material, namely, a three-layer boron-doped micro-crystalline, undoped micro-crystalline and undoped nano-crystalline composite diamond film, is deposited on the pretreated WC-6 wt% Co substrate, the basic characters of which are systematically studied and compared with some other commonly used diamond films. Besides, the growth times for three respective layers are accordingly determined. It is further clarified that the underlying boron-doped micro-crystalline diamond layer can well adhere to the WC-Co substrate due to either the reduction in the residual stress or the formation of B-Co compounds. There is no doubt that the surface undoped nano-crystalline diamond layer with relatively lower hardness and initial surface roughness is more convenient to be polished to the required surface roughness. Moreover, when the growth times for the middle undoped microcrystalline diamond layer and the surface undoped nano-crystalline diamond layer are both appropriate, the undoped micro-crystalline diamond layer with extremely high diamond quality and hardness can effectively reinforce the surface hardness of the whole composite film. Based on the discussions on the influences of the growth times for the different layers on the performance of the composite diamond film, the growth times for the boron-doped micro-crystalline diamond, undoped micro-crystalline diamond and undoped nano-crystalline diamond layers are, respectively, determined as 4, 4 and 2 h. Under such conditions, the reinforcement effect of the middle layer on the surface hardness can be guaranteed, and the undoped nano-crystalline diamond grains have totally covered the undoped micro-crystalline diamond layer.

Cutting performance evaluation of boron-doped and undoped diamond coatings in drilling of CFRP laminates

“…For incomplete agreement, other reasons for such adhesion phenomenon can be proposed. Wang et al 27 reported in their study that boron-doped NCD film, in which the compressive residual stress is lower than in undoped MCD film, shows a larger film removal area compared to the undoped MCD due to its poor mechanical cohesion. Therefore, a reduction in the residual stress caused by boron doping cannot compensate for the influence of diamond film impurities on its adhesion.…”

Adherent diamond coating deposited on Ti by ultrasonic after carbonization pretreatment

“…The adhesion of the diamond coatings were evaluated by Rockwell C indentation test using a 588 N load. [26][27][28] diamond forms a continuous film on the rough substrate surface with no substrate exposed. The phase composition of diamond coating was determined by Raman measurement, and the Raman spectra of diamond deposited on C1 sample were shown in Figure 1(b).…”

“…The adhesion of the diamond coatings were evaluated by Rockwell C indentation test using a 588 N load. 26–28…”

Fabrication and performance of boron doped textured diamond coated tool

“…The results indicated that boron doped can improve the adhesion strength of the film. The catalytic action of cobalt element in the substrate will be reduced owing to the stable B-Co compound formed in the process of CVD, thus the adhesion strength of the film has been improved [23,24]. Figure 6(c,d) shows the indentation morphology of BDETD and BDGTD films, respectively.…”