Microstructure Formation and Mechanical Properties of Multi-Phase Coating by Thermos Plasma Nitriding of Gradient Cu-Ti Films on C61900 Cu Alloy

Yandan Zhu,Quanli Zhang,Mufu Yan

doi:10.3390/app112210843

Abstract

To improve the processing efficiency and the surface properties of C61900 Cu alloy, a gradient Cu-Ti film with a Ti/Cu atom ratio of 7:1, 7:4, and 1:2 was pre-fabricated by the unbalanced magnetron sputtering process and then nitrided by thermos plasma nitriding. The phase structure, elemental composition, and morphology of the modified surface were characterized, and the mechanical properties, including the wear resistance and adhesion properties, were examined. Combining calculation by the first principle method with thermodynamic analysis, the microstructural formation and phase composition of the Cu-Ti-N system were investigated to reveal the mechanism of improved wear resistance, which indicated the possible formation of various Cu-Ti intermetallics and Ti-N compounds. The Al in the C61900 Cu substrate also participated in the generation of the AlCu2Ti compound, which is a ductile phase with good hardness and elastic modulus. Based on the results of a mechanical properties test, it was concluded that an optimized layer structure for the multi-phase coating should include Ti-N compounds as the surface layer and Cu-Ti intermetallics as the intermediate layer.

Highlights

The C61900 aluminum bronze alloy has been widely applied in the electronics, electrical, automotive, aviation, and astronautics fields
An intermediate Cu-Ti intermetallic layer is regarded as the most appropriate candidate to be the transition medium between the titanium nitride layer and the Cu substrate [9,10,11], where the formation of a thin TiN and Cu3Ti3O layer contributes to the improvement of wear resistance by plasma nitriding [12]
The intense peak at 2θ = 38.2◦ was from β-Ti rather than α-Ti, where the formation of β-Ti phase was promoted by the Cu substrate for the same body-centered cubic structure

Summary

Introduction

The C61900 aluminum bronze alloy has been widely applied in the electronics, electrical, automotive, aviation, and astronautics fields. Plasma nitriding of titanium alloys has been investigated to fabricate a titanium nitride layer for its excellent wear resistance and high hardness [5,6,7]. Fouquent et al investigated the plasma-assisted nitriding process on Ti-6Al-4V alloy, and they found that the main phases of the nitrided layer were δ-TiN, ε-Ti2N and the solid solution of N atoms dissolved in α-Ti [16]. The design and control of the phase compositions based on the first principle study have been rarely explored Both the phase stability and the mechanical properties of the Ti-N compounds and the Cu-Ti intermetallics have been investigated [28,29,30], but there are still few reports on the Ti-Cu-N and Ti-Al-Cu ternary systems that industry demands

Methods

Results

Conclusion