Investigation on the Performance of Al7075 Alloy Surface Repaired by Cold Spray Coating Technology

Repairing different waste parts is an attractive issue due to the cost of repaired parts is much lower than the cost produced by conventional methods. In this study, the Al7075 aluminium alloy surface was repaired using the Ni-Zn-Al2O3 powder by the cold spray coating method. The microstructure, micro-hardness, and tribological performance of the repaired zone were determined. The microstructure of repaired zone consisted of ceramic Al2O3 particles embedded in the Ni and Zn metal matrix, similar to a lamellar structure. The average microhardness value of the repaired area was about 4.3% higher than the Al7075 substrate. Although the average coefficient of friction had increased in the repaired area, the wear rate had decreased approximately 1.3 times. As a result of the FESEM examination of the wear channels, the main wear mechanism of the Al7075 material was abrasive, while the main wear mechanism of the sample repaired with cold spray coating was determined as adhesive wear. Consequently, it increases the service life of the part, as the repaired zone with cold spray coating shows approximately 1.3 times better wear performance than Al7075.

Study of the Effect of Thickness on the Residual Stress Profile of a Cold Spray Coating by Finite Element Analysis

The understanding of residual stress is of critical importance in the cold spray and thermal spray processes. It has a direct effect on the integrity of the coating related to the adhesion strength, fatigue life, and can lead to undesired effects such as the delamination of the coating. In cold spray, several investigations have evaluated the impact of the residual stress on the coatings, and it is generally accepted that cold spray coatings follow a similar profile to those obtained in the shot peening process. Although the measurement of residual stresses gives fundamental insight into the process, the estimation of such stresses considering the deposition of each layer by numerical methods has not been extensively studied. This work proposes a method for analyzing the evolution of residual stress on a cold spray coating, both on the coating and the substrate, as a function of the deposited layers, using Finite Element Analysis (FEA). The evolution of the residual stress profile with the coating thickness was obtained along the transverse direction. The results were compared to experimental and numerical data from previous studies. The influence of the deposition of each layer on the residual stress profile has been discussed.