Mechanical characterization of low‐pressure cold‐sprayed metal coatings on aluminium

Abstract

Metal coatings are widely used in order to improve the superficial properties of mechanical components or tools. Cold spray deposition is an attractive technology that allows to realize a reported coating on a metallic or polymeric surface. The essence of the phenomenon is that particles of ductile metals or alloys, having diameter of approximately 10-100 micron, become deformed and strongly attached to a surface when they impinge on the surface of metals, ceramics or glasses at impact velocities in the range of about 400-1200 m/s. In this manner, coatings can be formed on a substrate. In this work, mechanical tests were carried out in order to evaluate the adhesion of different metal particles on an aluminium alloy substrate, in order to characterize both the coating-substrate adhesion and the adhesion between two consecutive layers of the cold-sprayed metal coating. In particular, both bending tests and pure adhesion test were carried out in order to better understand the powder deposition mechanism. Bending tests were carried out in four-point bending configuration. On the basis of the experimental campaign, it results that the adhesion of the pure aluminum particles are very good, conversely the copper particles show a good adhesion on the aluminum substrate but have a low internal cohesion.

Selective Laser Treatment on Cold-Sprayed Titanium Coatings: Numerical Modeling and Experimental Analysis

“…The process involves the impact of solid particles at high velocity (about 500 to 1000 m/s) on substrate surface, promoting the mechanical bonding between the two materials. [4][5][6][7][8][9] Titanium cold-sprayed coatings on aluminum components showed to be effective in enhancing corrosion resistance, wear properties, and compatibility with CFRP, without affecting the temper status of the substrate. One main drawback of the use of the cold spray process, however, is related to the micro-porosity induced within the coating layer, negatively affecting the performance of the titanium layer as corrosion barrier.…”

On the Improvement of AA2024 Wear Properties through the Deposition of a Cold-Sprayed Titanium Coating

“…The macroscopic plastic deformation, induced by the high velocity impact, was indicated by some researchers as the main bonding mechanism [2,3]. Two different scenarios have been observed, depending on material pairing and particle velocity: (a) particles rebounding from the substrate or (b) particles bonding to the substrate [4]. The velocity at which bonding is achieved is referred to as the critical velocity and relies on the particle size and distribution as well as the substrate material.…”

Repairing of an Engine Block Through the Cold Gas Dynamic Spray Technology

“…Furthermore, it is possible to assess from Figure 9 that the welding repair showed an electrochemical behavior similar to the one of the base material while the OCP potential of the cold spray repair is noticeably lower than the previous ones. This result suggests an anodic behavior of the cold spray repaired zone with respect to the material of the engine block 8 . The general trend of the curve is similar for all the three samples under investigation.…”

“…In particular, in both cases it is possible to observe the occurrence of classical pitting 8,13 . The cold spray repair shows a better behavior with respect to the welded repair, in particular very few pits are appreciable.…”

“…When the particle hit the substrate the high kinetic energy causes a phenomenon of macroscopic plastic deformation that embeds the particle on the substrate while preserving its crystalline structure 7 . For the bonding to succeed it is necessary that the kinetic energy of the single particle is higher than a threshold value 8,9 . The velocity at which the bonding is achieved is called critical velocity and it is function of the particle size and distribution as well as the substrate material.…”