Wear behavior of diamond-coated drawing dies

Abstract

Abstract：The failure behavior of diamond-coated die was investigated experimentally and analytically through finite element method (FEM) simulation in the present work. Diamond coatings were fabricated by straight hot filament chemical vapor deposition (CVD) passing through the interior hole of the drawing die using a mixture of hydrogen and acetone as source gases. The performance tests were made under real drawing condition. Scanning electron microscopy (SEM) was used for the study of coating wear after die service. The coating wear appears on two regions of the reduction zone: one is near the entrance where the contact begins, and the other is at the end of the reduction zone. FEM simulation was made for calculating the von Mises stresses distribution on the coating and substrate during the drawing process. The present work was of great practical significance for the improvement of drawing performance of diamond-coated drawing dies.The die holes of drawing dies are required to have high surface hardness for drawing metal wires, especially for hard metals, so as to ensure the dimensional precision, smoothness of the drawn metal wires and increase the drawing die working lifetime. An effective method is to deposit a uniform diamond thin film on the interior hole surface of the WC-Co drawing dies, as the thin film diamond chemical vapor deposition (CVD) technology gradually matures. In recent years, a number of studies on the fabrication of diamond-coated drawing dies and characterization of diamond coating have been conducted. Zhang et al [1] investigated the fabrication of diamondcoated drawing dies by the hot filament CVD method. The surface morphology and thickness of diamond coating were analyzed by scanning electron microscopy (SEM) and Raman spectroscopy at different positions on the die hole surface. Sun et al [2] developed a new technology to fabricate the nanocrystalline and microcrystalline composite diamond films on the die hole surface by a two-step CVD procedure. The effects of pretreatment methods and chamber pressure on morphology, quality and adhesion of HFCVD diamond coating retreatment were studied [3] . Furthermore, tribological and wear behaviors were investigated. The influences of diamond fiber textures and surface roughness were studied through planar sliding experiments of self-mated CVD diamond coatings in dry ambient atmosphere [4,5] . An experimental and numerical approach was employed by Schmitt and Eleöd [6] to study tribological behavior of diamond coatings sliding against steel.On the other hand, a number of studies on cold drawing were also made. FEM simulation and experiment methods were employed to analyze the deformation, strain and stress that are involved in the wire drawing process [7][8][9][10] , tube sinking drawing [11][12][13] and floating plug drawing [14][15][16] . However, the wear behavior of diamond-coated die drawing metal wire has less been investigated. The main objective of this work is to explore the wear behaviors of CVD diamond-coated drawing dies.In the pre...

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