Impact of Impulse Shot Peening Parameters on Properties of Stainless Steel Surface

et al. 2021

Materials

The paper presents the results of experimental studies on the impact of impulse shot peening parameters on surface roughness (Sa, Sz, Sp, Sv), surface layer microhardness, and the mean positron lifetime (τmean). In the study, samples made of the Inconel 718 nickel alloy were subjected to impulse shot peening on an originally designed stand. The variable factors of the experiment included the impact energy, the diameter of the peening element, and the number of impacts per unit area. The impulse shot peening resulted in changes in the surface structure and an increase in surface layer microhardness. After the application of impulse shot peening, the analyzed roughness parameters increased in relation to post-milling values. An increase in microhardness was obtained, i.e., from 27 HV 0.05 to 108 HV 0.05 at the surface, while the maximum increase the microhardness occur at the depth from 0.04 mm to 0.08 mm. The changes in the physical properties of the surface layer were accompanied by an increase in the mean positron lifetime τmean. This is probably related to the increased positron annihilation in point defects. In the case of small surface deformations, the increase in microhardness was accompanied by a much lower increase in τmean, which may indicate a different course of changes in the defect structure consisting mainly in modification of the dislocation system. The dependent variables were subjected to ANOVA analysis of variance (it was one-factor analysis), and the effect of independent variables was evaluated using post-hoc tests (Tukey test).

Section: Introductionmentioning

confidence: 99%

Analysis of Surface Properties of Nickel Alloy Elements Exposed to Impulse Shot Peening with the Use of Positron Annihilation

et al. 2021

Materials

“…During shot peening, the concentration of crystal structure defects changes, as confirmed in tests that were carried out by annihilation techniques [32], as a result of which compressive stresses form in the surface layer of the workpiece [33]. Changes in the state of residual stress and the increase in the microhardness of the surface layer enhance the resistance of the material to abrasive and fatigue wear [34,35].…”

Section: Introductionmentioning

confidence: 99%

Effect of Centrifugal Shot Peening on the Surface Properties of Laser-Cut C45 Steel Parts

2019

Materials

This article presents the results of experimental studies of the impact of centrifugal shot peening parameters on the roughness, microstructure, and microhardness of the surface layer of laser-cut C45 steel parts. Residual stress distributions and the presence of iron oxides on the surface of these elements were also examined. Centrifugal shot peening tests were performed on an FV-580a vertical machining center while using a specially designed peening head. The parameters that were varied during centrifugal shot peening included tangential speed of the tool vg and feed rate vf. The use of centrifugal shot peening for finish machining of laser-cut C45 steel parts allowed for obtaining a four-fold reduction in the surface roughness parameters Ra and Rz. As a result of shot peening, the geometrical structure of the surface of the steel parts was modified and it acquired new beneficial features, such as large values of the rounding radii of the micropeaks and high material ratios (Rmrmax = 92%). At the same time, the surface layer was hardened (microhardness increased by 16%) and a compressive residual stress layer was produced on the surface of the workpieces. Additionally, as the shot impacted the processed surface, combustion products were “blasted” or “sheared” off it. Shot peening using the proposed technique can be successfully performed while using CNC machines.

“…Static burnishing and shot peening cause changes in the workpiece surface roughness, make the surface layer strainhardened and generate compressive residual stresses [1,2,3,4]. These changes in surface layer properties are associated with higher density of defects in the crystalline structure, as confirmed by the studies performed by annihilation techniques [5,6].…”

Section: Introductionmentioning

confidence: 86%

Effect of Slide Burnishing on the Surface Layer and Fatigue Life of Titanium Alloy Parts

Advances in Materials Science

2019

Self Cite

The paper presents the results of a study investigating the effect of slide burnishing on the surface roughness, surface layer microhardness and fatigue life of Ti6Al2Mo2Cr titanium alloy parts. The burnishing process was performed with the use of a diamond tip tool. Different machining fluids were used as machining media. Prior to burnishing, the samples were subjected to turning. The burnishing process led to reduced surface roughness (average roughness Ra decreased by 3.5 times and roughness Rz decreased by 2.5 times) as well as increased surface layer microhardness (microhardness maximum increase by 12%) and fatigue life of the tested parts. A relationship between the machining medium and the burnishing effects was also observed. The addition of a surface-active polymethyl methacrylate solution to the machining medium led to an increase in the surface layer microhardness and fatigue life of the workpiece.