Interpretation of the hardness of worn DLC particles using micro-Raman spectroscopy

Minute DLC particles may be generated during running of DLC-coated rolling elements and cause further damage on the subsequent running. Their hardness, which is a key parameter in wear is, however, impossible to measure by conventional means. Are they as hard as the original DLC coating or softened by frictional heat? This paper proposes to make use of the Raman intensity ratio (ID/IG) to infer hardness of the tiny DLC particles. The Raman spectroscopy ultilizing laser as the light source makes it suitable for measurements on micron-sized particles.