Effect of gradient buffer layer prepared with different substrate bias on the adhesion of cBN film deposited by R.F. magnetron sputtering with B4C target and unipolar pulsed D.C. substrate bias
- Effect of gradient buffer layer prepared with different substrate bias on the adhesion of cBN film deposited by R.F. magnetron sputtering with B4C target and unipolar pulsed D.C. substrate bias
- 이승민; 백영준; 이욱성; 성태연; 박종극
- cBN; gradient layer; adhesion; B4C; sputtering
- Issue Date
- 10th APCPST (Asia Pacific Conference on Plasma Science and Technology)
- cBN (cubic boron nitride) shows outstanding mechanical properties such as hardness and wear resistance. In contrast to diamond, cBN is compatible with ferrous materials, which makes it possible to be used as coating materials for machining of ferrous materials at high temperatures. However, amorphous BN and hBN layers inevitably formed before nucleation of cBN weaken the interface stability between cBN film and substrate. Furthemore high stress developed during deposition of cBN film deteriorates adhesive strength of cBN film. These poor stability and adhesion should be outcome to use cBN as protective coating material. Recently, many methods such as adoption of buffer layer and addition of oxygen have been suggested to improve the interface stability and adhesion of cBN film. In this study, we have investigated the effect of composition and bias graded buffer layer on the adhesion improment of cBN film. The buffer layer and cBN film was prepared by reactive magnetron sputtering of B4C target with Ar-N2 reactive gases of various volume retios. The chamber pressure was controlled to be 2mtorr. Unipolar pulsed D.C. bias was applied to the substrate during deposition. The adhesion of cBN film was greatly improved by adoption of compositionally graded buffer layer. However, the adhesion i,provement of cBN filmis critically dependent on the substrate bias applied during the deposition of buffer layer. With the decrease in substrate bias, the delamination of film was observed to occur in the compositionally graded buffer layer. On the contrary, the buffer layer deposited with substrate bias over-200V plays an important role in improving adhesion of post-deposited cBN film. This behavior was discussed in terms of the interface morphology and bonding structure in the compositionally graded buffer layer prepared.
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