Semi-quantitative chemical analysis of hard coatings by Raman micro-spectroscopy: the aluminium chromium nitride system as an example

摘要

A new method for chemical analyses of nitride-based hard coatings is presented. Raman band shifts in the spectra of Al x Cr1?x N coatings, deposited by physical vapour deposition from Al x Cr1?x targets with x T,Al = 0, 0.25, 0.50, 0.70 and 0.85, are calibrated using compositional data of the coatings derived by elastic recoil detection analysis (ERDA) and electron probe micro-analysis (EPMA). Inserting the composition-dependent Raman shift of a combinatorial acoustic-optic lattice mode into an empirically derived equation allows the determination of Al/Cr ratios of the coating with an accuracy of about ±2%. Spot, line and area analyses of coated cemented carbide and cold work steel samples by using a computer-controlled, motorized x,y-stage are demonstrated and the most important errors influencing precision and accuracy are discussed.