Surface, Subsurface and Tribological Properties of Ti6Al4V Alloy Shot Peened under Different Parameters

Effects of Shot Peening and Electropolishing Treatment on the Properties of Additively and Conventionally Manufactured Ti6Al4V Alloy: A Review

This literature review indicates that the basic microstructure of Ti6Al4V is bimodal, consisting of two phases, namely α + β, and it occurs after fabrication using conventional methods such as casting, plastic forming or machining processes. The fabrication of components via an additive manufacturing process significantly changes the microstructure and properties of Ti6Al4V. Due to the rapid heat exchange during heat treatment, the bimodal microstructure transforms into a lamellar microstructure, which consists of two phases: α' + β. Despite the application of optimum printing parameters, 3D printed products exhibit typical surface defects and discontinuities, and in turn, surface finishing using shot peening is recommended. A literature review signalizes that shot peening and electropolishing processes positively impact the corrosion behavior, the mechanical properties and the condition of the surface layer of conventionally manufactured titanium alloy. On the other hand, there is a lack of studies combining shot peening and electropolishing in one hybrid process for additively manufactured titanium alloys, which could synthesize the benefits of both processes. Therefore, this review paper clarifies the effects of shot peening and electropolishing treatment on the properties of both additively and conventionally manufactured Ti6Al4V alloys and shows the effect process on the microstructure and properties of Ti6Al4V titanium alloy.

Effect of Shot Peening on the Strength and Corrosion Properties of 6082-T651 Aluminium Alloy

This paper investigated the effect of shot peening on the strength and corrosion properties of 6082-T651 aluminium alloy. The microstructure, surface roughness, microhardness, residual stresses, and corrosion behaviour were investigated and compared with those of untreated aluminium alloy. Cracks and delaminations in the surface layer could only be seen on the treated specimens at a working pressure of 4 bar and 8 bar, while no such effect was observed at a working pressure of 1.6 bar. The surface roughness was increased more than 15 times after shot peening at a working pressure of 8 bar. Shot peening resulted in an increase in microhardness of 27% and a deeper layer with higher compressive residual stresses compared to the untreated specimens. All treated specimens exhibited improved corrosion resistance with a lower degree of anodic dissolution. The current density of the treated specimen with the lowest surface roughness was more than two-fold lower than that of the untreated specimen.

Tribological Properties of Ti6Al4V Alloy Composite Texture Fabricated by Ultrasonic Strengthening Grinding and Laser Processing

The Ti6Al4V alloy has been widely used in aerospace equipment and medical devices. However, the poor wear resistance of the Ti6Al4V alloy hinders its further engineering application. In this study, the ultrasonic strengthening grinding process (USGP) and laser texturing process were employed to enhance the wear resistance of Ti6Al4V alloy. The frictional behavior of all samples was determined via a ball-on-disc friction and wear tester under dry conditions. The worn surface morphology, cross-sectional hardness, surface roughness, and microstructure were analyzed. The results demonstrated that the USGP induced high hardness, high dislocation density, and grain refinement, as well as improvements in the wear resistance of Ti6Al4V. Moreover, laser texture could enhance the capacity to capture wear debris and reduce wear probability. When combining the USGP and laser texturing process for the surface treatment of Ti6Al4V alloy, the lowest and most stable friction coefficients were obtained, as well as the best wear resistance. Compared to the polished sample, the steady stage friction coefficient of the sample treated by USGP and laser texturing process was remarkably decreased by 58%. This work demonstrates that combining the USGP and laser texturing process could be a promising solution for improving the wear resistance properties of Ti6Al4V alloy, which makes it more suitable for various engineering applications.

Effects of Shot Peening and Cavitation Peening on Properties of Surface Layer of Metallic Materials-A Short Review

Shot peening is a dynamically developing surface treatment used to improve the surface properties modified by tool, impact, microblasting, or shot action. This paper reviews the basic information regarding shot peening methods. The peening processes and effects of the shot peening and cavitation peening treatments on the surface layer properties of metallic components are analysed. Moreover, the effects of peening on the operational performance of metallic materials are summarized. Shot peening is generally applied to reduce the surface roughness, increase the hardness, and densify the surface layer microstructure, which leads to work hardening effects. In addition, the residual compressive stresses introduced into the material have a beneficial effect on the performance of the surface layer. Therefore, peening can be beneficial for metallic structures prone to fatigue, corrosion, and wear. Recently, cavitation peening has been increasingly developed. This review paper suggests that most research on cavitation peening omits the treatment of additively manufactured metallic materials. Furthermore, no published studies combine shot peening and cavitation peening in one hybrid process, which could synthesize the benefits of both peening processes. Moreover, there is a need to investigate the effects of peening, especially cavitation peening and hybrid peening, on the anti-wear and corrosion performance of additively manufactured metallic materials. Therefore, the literature gap leading to the scope of future work is also included.

Modification of Surface and Subsurface Properties of AA1050 Alloy by Shot Peening

AA1050 Al alloy samples were shot-peened using stainless-steel shots at shot peening (SP) pressures of 0.1 and 0.5 MPa and surface cover rates of 100% and 1000% using a custom-designed SP system. The hardness of shot-peened samples was around twice that of unpeened samples. Hardness increased with peening pressure, whereas the higher cover rate did not lead to hardness improvement. Micro-crack formation and embedment of shots occurred by SP, while average surface roughness increased up to 9 µm at the higher peening pressure and cover rate, indicating surface deterioration. The areal coverage of the embedded shots ranged from 1% to 5% depending on the peening parameters, and the number and the mean size of the embedded shots increased at the higher SP pressure and cover rate. As evidenced and discussed through the surface and cross-sectional SEM images, the main deformation mechanisms during SP were schematically described as crater formation, folding, micro-crack formation, and material removal. Overall, shot-peened samples demonstrated improved mechanical properties, whereas sample surface integrity only deteriorated notably during SP at the higher pressure, suggesting that selecting optimal peening parameters is key to the safe use of SP. The implemented methodology can be used to modify similar soft alloys within confined compromises in surface features.