Abstract A methanol pretreating method was proposed to reduce the Co concentration on the surface of WC-Co substrate;also a new two.step chemical procedure combined with methanol pretreating method was put forward to increase the diamond nucleation density and the adhesion strength between the diamond films and the substrates.High quality diamond films were deposited on such pre-treated substrates by hot filament chemical vapor deposition(HFCVD)method using a mixture of acetone and hydrogen gases.The surface morphologies,nucleation density,diamond films and composition were observed with different techniques.Drilling bits were given as an example to verify the effect of the new two-step chemical procedure on the pretreatment of WC-Co substrate and diamond films.The results showed that the new two-step method increases the diamond nucleation density and enhance the adhesion strength greatly.The new two-step chemical procedure is very suitable for complex shaped substrates,such as rotational cutting tools and drawing dies,which may broaden the use of diamond coatings for coated tool applications.

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