J. Nebel, E. Vogli, W. Tillmann, TU Dortmund, Dortmund, Germany
Detonation spraying provides the ability to produce superabrasive diamond grinding tools. Especially the atmospheric conditions of the spraying process yield to a high production flexibility. However, oxygen atmosphere, thermal and kinetic energy during the detonation spraying have an impact on the processed diamond. Despite its importance for the tools performance, the influence of the spraying process on the diamond is not determined up to now. The effect of the detonation spray process on the diamonds was identified by analytical measurements and process diagnostics. Differential thermal analysis, X‑Ray diffraction, Raman spectroscopy, and friability-tests were used to verify surface reactions, residual stress behaviour, and the durability of the sprayed diamonds after exposure to the spraying process.
It was found that spraying process optimization can minimize deterioration appearances. The thermal and mechanical impact during the detonation processing can remain low enough to ensure a good reliability of the processed diamonds.
A good grinding performance of sprayed diamond-CuSn 85/15 composite tools was pointed out in grinding tests. Additionally, the grinding test results are correlated to vacuum sintered diamond-CuSn 85/15 tools.
Summary: The strength of the diamond particle is one of the most important factors influencing the performance and durability of diamond composite tools. Diamond deterioration such as oxidation, graphitization, cracking or chemical reactions with the matrix material reduces this strength. The effect diamond deterioration during the production of detonation sprayed diamond-CuSn 85/15 composites under atmospheric conditions is predominantly unknown.
Analytical investigations on detonation sprayed diamonds and process diagnostics on the spraying process showed opportunities and limitations in the spraying of diamonds. Therefore, superabrasive diamond composite coatings were produced by detonation spraying. Diamonds of a grain size 60-70 Mesh and 120-140 Mesh were used as superabrasive. CuSn 85/15 (45-90 µm) was taken as matrix material.
Extracted diamonds after detonation spraying were investigated regarding to their properties. The thermal and mechanical influence on the diamonds were characterized and evaluated.
It was detected that the thermal energy of the detonation only affected a small amount of the diamond surface. The diamond crystal structure endure the spraying process almost without graphitization or oxidation. A high durability and grinding performance of the sprayed diamond composite were confirmed in grinding tests.
