Soft g-C3N4 phases in amorphous CNx coatings

Abstract

Carbon-Nitride (CNx) coatings deposited using plasma-based physical and chemical vapor deposition led to the formation of g-C3N4 phase in crystalline and mainly amorphous forms respectively, Nanoindentation was performed on these coatings deposited on 304 SS (stainless steel) substrates. The positioning of the indentation i.e. inside the grain formed and at the boundary showed prolific features about the understanding of the extension of plastic volume and variations in interfacial fracture energies and the role played by ductile substrates in preventing damage to a component. The softer CVD-grown g-C3N4 phase, due to its larger grain size provides lubrication, wear resistance, and protection against chemical attack to the steel substrate underneath at the same time causing nanoindentation-induced strain hardening in it. The grain boundary regions as compared to grain center regions. were susceptible to failure due to their amorphous nature found in both PVD-grown g-C3N4 coatings. This inhomogeneous behavior is detrimental to the overall performance of the system as confirmed by the strain rate variations. A heat treatment post-deposition leading to crystallization and grain growth can improve the coating quality.

Keywords

• CNx
• g-C3N4
• Nanoindentation
• Low hardness
• Substrate effect