Fabrication and application of boron-doped diamond coated rectangular-hole shaped drawing dies

• Deposition parameters on the rectangular-hole surfaces are optimized.
• Boron doped diamond coated rectangular-hole shaped drawing dies are fabricated.
• BDD film exhibits better adhesion and surface smoothness than the undoped one.
• BDD coated dies present favorable erosion performance and application effects.

Recently, shaped drawing dies with complicated hole shapes have attracted intensive interests to produce shaped wires. In order to produce high-quality wires, the surface smoothness of the drawing dies is a major requirement and as important as the wear resistance. In the present investigation, the deposition parameters in diamond films growth on the interior-hole surfaces of the WC–Co rectangular-hole shaped drawing dies are optimized by orthogonal simulations, for which homogeneous substrate temperature (dT < 15 °C) and gas density fields are obtained. Thereafter, boron-doped diamond (BDD) films are fabricated and characterized, showing that high-quality films with uniform thickness (24–25 μm) have been deposited on the whole interior-hole surface. Compared with the undoped diamond film, the BDD one presents much better adhesion and long-tested wear resistance. Moreover, the BDD film is also much easier to be polished to the appropriate surface smoothness due to the grain refinement and hardness reduction. Particularly, by comparison to the WC–Co drawing die, the working lifetime of the BDD coated one increases by a factor of above eight and in the course of processing, copper rectangular wires with higher surface quality and better dimensional precision are obtained.