Wear properties, corrosion behaviors, and TEM structures of CrSiN/CrSi multilayer coatings on oxynitriding-treated Unimax tool steel using the direct current magnetron sputtering system

Abstract

This study employed the direct current magnetron sputtering process of physical vapor deposition to deposit CrSiN and CrSiN/CrSi multilayer coatings onto Unimax tool steel post oxynitriding treatment. Experimental parameters included various deposition times (1.5, 2, 2.5, and 3 h), a gas flow rate of 45/30 (Ar/N₂) sccm, a power of 100 W, a voltage of 400 V, a substrate bias of −50 V, and a deposition temperature of 250 °C. The results indicate that when deposited for 2.5 h, the CrSiN coatings exhibited a distinct columnar crystal structure and possessed the highest hardness (14.0 GPa) and elastic modulus (241 GPa). When the deposition times were 10 min for CrSi and 2 h and 20 min for CrSiN, the CrSiN/CrSi multilayer coatings demonstrated the best wear resistance (with a wear loss volume of 1.5 × 10⁻⁴ mm³ and a specific wear rate of 5.2 × 10⁻⁸ mm³·m⁻¹ N⁻¹ under a 5 N load) and strong corrosion resistance (with a corrosion current of 5.2 × 10⁻⁶ A·cm⁻² and polarization resistance of 783 Ω cm² in a 3 wt% NaCl solution). Transmission electron microscopy observations reveal that the CrSiN/CrSi multilayer coatings exhibited a stable CrN crystal structure alongside Si₃N₄ amorphous structures.