Microstructure and Mechanical Properties of Cr-Al-B-N Coatings Prepared by Reactive D.C. and R.F. Co-Sputtering

Abstract

The current study was undertaken to investigate the synthesis of CrAlN/BN composite coatings having super high hardness by a reactive co-sputtering using CrAl alloy and BN targets and gaseous mixture of Ar+N2, in order to eliminate the possible formation of boride bonding. CrAlN or BN phase was deposited by pulsed d.c.- and r.f.- sputtering, respectively. Plastic hardness, Hpl, and Young’s modulus, E*, of the coatings increased with BN phase ratio, reaching a maximum value of ~46 GPa and 390 GPa at ~8 vol. % of BN phase; and then decreased to ~20GPa and ~300GPa at ~18 vol.%, respectively. Only B1 structured Cr(Al)N phase was found in XRD and SAED analysis. XPS and TEM/HRTEM results revealed that the CrAlN/8vol%BN coating consists mostly of CrAlN and BN phase, which exists as an amorphous like phase among the CrAlN grains. The CrAlN/8vol%BN coating has a kind of nanocomposite structure and the super high hardness over 40 GPa is probably due to this structure.

Effect of Silicon Concentration on the Properties of Al-Cr-Si-N Coatings Deposited Using Cathodic Arc Evaporation

“…Many authors indicated that even a small addition of another element to the coating significantly affects the size of the crystallites. Nose et al found that an increase in the concentration of boron in the AlCrN coating causes a reduction of crystallites oriented in the (111) plane from about 23 nm to about 10 nm and in the (200) plane from about 12 nm to about 5 nm [ 39 ]. Tritremmel et al confirmed the decrease in the crystallite size from about 35 nm to about 6 nm in AlCrSiN coatings produced by cathodic arc evaporation from AlCrSi cathodes, in which Al/Cr = 1 and the silicon concentrations from 0 to 20 at% [ 11 ].…”