Fretting Wear and Scratch Resistance of Cold-Sprayed Pure Cu and Ti

Rodolpho F Váz,Pasquale D Cavalière,Antonella Rizzo,Alessio Silvello,Sergi Dosta,Laura Capodieci,Irene G Cano,Daniele Valerini

doi:10.1007/s13632-021-00758-2

Abstract

The paper analyses the fretting and wear behavior of pure copper and pure titanium coatings realized through cold spray. The coatings were designed and produced by employing processing conditions leading to minimum porosity and high hardness; these conditions were 700 °C and 40 bar for Ti powders and 400 °C and 30 bar for Cu ones. The low porosity and high strength materials led to high resistance to wear damaging through the optimal energy dissipation upon fretting. Due to the sprayed particles deformation mode, the sprayed materials show non-uniform hardening along the deposition distance. As a matter of fact, hardness varied in the range 3.7–4.2 GPa for Ti coatings and 1.5–2 GPa for the Cu ones depending on the distance from the substrate and on the coatings thickness. This influenced the materials properties and the response to the wear damaging. This was demonstrated by the scratch tests performed on coatings with different thicknesses. Those coatings sprayed in major thickness revealed the best wear resistance due to the deformation hardening. The harder coatings also revealed brittle fracture at the experienced highest loads.

Highlights

Cold spray is recognized as an optimal additive manufacturing (AM) technology capable of producing sound bulk components [1,2,3,4] with exceptional performances experienced by copper, nickel- and titanium-based materials [5,6,7,8,9]
The porosity of Cu coatings was lower than the values presented by Yin et al [7] and Huang et al [28], who obtained the best value of 1.67 ± 0.21% and 0.8 ± 0.4%, even with higher temperature, 650 and 800 °C, respectively, than the used in this work
By tuning an ideal impact velocity, a very high particles flattening is obtained and a reduction of the deposit porosity can be recorded. This is accompanied with the particle–particle voids filling as the severe plastic deformation increases [42]

Summary

Introduction

Cold spray is recognized as an optimal additive manufacturing (AM) technology capable of producing sound bulk components [1,2,3,4] with exceptional performances experienced by copper-, nickel- and titanium-based materials [5,6,7,8,9]. The sprayed particles severely deform upon impacting on hard substrates leading to compact deposits This low-temperature thermal spray technology avoids undesirable oxidation processes or phase modifications in the sprayed materials leading to the obtaining of components characterized by good mechanical properties [10]. The activated microstructural features are dependent on the sprayed particles properties, the substrate surface and mechanical properties and the employed pressure and temperature of the spray gases As these properties are varied, different coatings behaviors are expected [12]. Many scientific evidences underline that the particle–particle cohesion is due to the achievement of the adiabatic shear instability This phenomenon leads to local temperature increase supporting the particle deformation that behaves as a viscous material. Processing conditions influence the severe plastic deformation levels; this governs the

Methods

Results

Conclusion