Plateholder design for deposition of uniform diamond coatings on WC-Co substrates by microwave plasma CVD for efficient turning application

摘要

Polycrystalline diamond coatings have been grown on cemented carbide WC-6% Co substrates with different aspect ratios by microwave plasma CVD in CH4/H-2 gas mixtures. Special plateholder with holes for group growth has been used to protect the edges of the substrates from non-uniform heating due to the plasma edge effect. The difference in heights Delta h of the substrates and plateholder, and its influence on the diamond film mean grain size, growth rate, phase composition and stress was investigated. Diamond growth rate of 0.3-1 mu m/h and compressive stress of 2.2-2.5 GPa, respectively were determined in the optimal Delta h region. The substrate temperature range of 740-760 degrees C, within which uniform diamond films are produced with good adhesion, is determined. The diamond-coated samples produced at optimized process conditions exhibited a reduction of cutting force and wear resistance by a factor of two, and increase of cutting path length up to 8150 m or by 4.3 times upon turning A390 Al-Si alloy as compared to performance of uncoated tools.