Improving Corrosion Resistance Properties of Nickel-Aluminum Bronze (NAB) Alloys via Shot Peening Treatment

Abstract

In this paper, Nickel-Aluminum Bronze (NAB) alloy was subjected to the shot-peening (SP) treatment, and the corrosion resistance properties of SPed NAB alloy was systematically studied by scanning electron microscope, transmission electron microscopy, electrochemical workstation and immersion tests. The results show that SP treatment can improve the corrosion resistance properties of NAB alloy by controlling shot peening intensity. The SP treatment can result in rough surfaces, high-density dislocations and grain refinement of ¡ and ¢A martensitic phases in NAB alloy surface. In the corrosion medium, the corrosion resistance properties of SPed NAB alloys are related to not only the surface microstructures but also the surface roughness. The refined and homogenized microstructures favors the rapid formation of the protective passive film and promotes the occurrence of uniform corrosion on shot-peened NAB alloy surface, thus significantly improving their corrosion resistance properties. However, as the shot-peening intensity exceeds a critical value, the higher roughness values due to the large cracks, chips and flaking appearing on the shot-peened sample surface can deteriorate corrosion resistance properties.

Fabrication of MnCuNiFe–CuAlNiFeMn Gradient Alloy by Laser Engineering Net Shaping System

“…Al 2 O 3 is denser than Cu 2 O and has no electrical conductivity. It can effectively isolate the NAB matrix from the corrosive medium 3.5% NaCl solution and block its charge exchange, thereby providing better protection [ 41 , 42 ]. The reaction equation is: …”

A review of the corrosion behavior of conventional and additively manufactured nickel–aluminum bronze (NAB) alloys: current status and future challenges

“…103 Table 9 also reports that post-processing strategies can enhance the corrosion performance of NAB alloys. For example, shot-peening of NAB surfaces 101,102 has been shown to increase corrosion resistance of the alloy up to a critical peening intensity, ascribed to enhanced passivity. However, exceeding the critical intensity results in more severe corrosion due to rougher surface and higher effective surface area.…”

“…76 For instance, shot peening, a surface severe plastic deformation method, has been found to influence the corrosion properties of NAB. 101 Shot-peened samples exhibited improved corrosion resistance compared to the non-treated alloy, attributed to the increased density of short-circuit diffusion paths, such as grain boundaries and twins, which facilitate the rapid formation of a passive film. However, excessive shot-peening intensity beyond a critical value resulted in decreased corrosion resistance due to higher roughness values caused by surface irregularities, such as cracks, which led to the formation of a defective passive film on the alloy surface, 101 consistent with previous findings.…”

“…101 Shot-peened samples exhibited improved corrosion resistance compared to the non-treated alloy, attributed to the increased density of short-circuit diffusion paths, such as grain boundaries and twins, which facilitate the rapid formation of a passive film. However, excessive shot-peening intensity beyond a critical value resulted in decreased corrosion resistance due to higher roughness values caused by surface irregularities, such as cracks, which led to the formation of a defective passive film on the alloy surface, 101 consistent with previous findings. 102 Similarly, friction surfacing, another commonly used surface treatment method where a coating material is applied onto a substrate, was shown to negatively impact the corrosion resistance of NAB under salt spray fog testing condition (ASTM B117).…”

“…85,91,93 Similarly, inducing higher levels of residual compressive stress (up to an optimum value) and defect density (e.g., grain boundary density) through shot peening can yield similar results. 101 In addition to oxide films, the formation of non-oxide films and their integrity can also affect the corrosion properties of NAB alloys. For instance, despite the negative impact of the presence of sulfide in the solution on the corrosion performance of NAB, the formation of a relatively uniform corrosion product film in a solution with 200 ppm sulphide can moderately improve the corrosion resistance of the alloy.…”