Effect of Silicon Additions in CrSi (10, 20, 30, 40 at. Si) Magnetron Targets on Microstructure of Reactively Deposited (Cr,Si)N Coatings

摘要

The CrSi compacts containing 10, 20, 30 and 40 at.% Si sintered from mixed elemental powders were used as targets for reactively deposited magnetron (Cr,Si)N coatings. The silicon substrates were kept either at ambient temperature or heated up to 600°C. The microstructure observations were performed using TECNAI FEG (200 kV) with EDAX X-ray Energy Dispersive Spectroscopy (EDS) system and JEOL 3010 (300 kV) with Gatan Energy Filtering (GIF) attachment microscopes. The thin foils were cut using QUANTA Focused Ion Beam (FIB) system. The performed investigations proved that increasing silicon content in coatings deposited at 600°C using CrSi10, CrSi20 and CrSi30 targets caused a refining of their fully crystalline CrN-type columnar microstructure from ～ 40 to ～ 35 and ～ 25 nm. The deposition performed from the same targets, but at ambient temperatures, i.e. without resistive heating of the substrates, produced coatings of mixed crystalline-amorphous type. They were characterized by gradient microstructure with amorphous material prevailing close to the substrate, but vanishing higher up. The rising of silicon content in the targets resulted in decreasing amount of crystalline phase. The coatings obtained from Cr40Si target were fully amorphous independently of substrate temperature during deposition. The measurements of local chemical compositions obtained using EDS technique indicated that the Cr:Si ratio in the coatings roughly reproduced that present in the targets used for their deposition. Additionally, these measurements indicated that all coatings are contaminated with oxygen. The mapping of chemical composition using GIF technique of mixed crystalline-amorphous coatings proved that they are enriched in Cr and Si, respectively. The present results showed, that relying on single CrSi target magnetron sputtering the crystalline-amorphous nanocomposite could be obtain at silicon additions from 10 to 30 at %, being well above were that type of microstructure is formed during deposition using double target magnetron systems. Additionally, for the first time, the measurements helped to prove that the crystallites and amorphous material are enriched in chromium and silicon respectively, i.e. confirmed presence of CrN/Si_3N_4 composite.