Research on the growth state and performance of diamond coatings based on different carbon source concentration and temperature

Abstract

In this paper, diamond coatings with different microstructure were prepared on cemented carbide substrates by HFCVD technique. The changes of grain growth mode and size of diamond coating under different substrate temperature (800 °C, 850 °C, 900 °C) and carbon source concentration (2%, 4%, 6%) were studied, and the differences of coating performance were explored. Both substrate temperature and carbon source concentration have an effect on grain size. When the grain size is in micron scale (0.5 ∼ 6 μm), the growth mode is columnar crystal competing growth. When the substrate temperature reaches 900 °C and the carbon source concentration is 6%, the diamond grain will be fully secondary nucleated, and the grain size will reduce to the nanometer scale (20 ∼ 50 nm). The growth mode is particle cluster accumulation growth and the rate of growth increases significantly. The increase of grain size will increase the adhesion of the coating and its resistance to wear and external loading. However, it may lead to larger friction coefficient, which is about 0.1. Due to the small grain size, the adhesion force of nanocrystalline diamond coating is obviously smaller than micrystalline diamond coating, but the friction coefficient is only 0.03.