Peening

About: Peening is a research topic. Over the lifetime, 5538 publications have been published within this topic receiving 73073 citations.

Estimation of residual stress and its effects on the mechanical properties of detonation gun sprayed WC–Co coatings

Abstract: It is essential to analyze the residual stresses of thick coatings since they seriously affect coatings' performance during their service. It is also important to understand the mechanisms by which the stresses arise, to predict and control the stresses for improving coating properties. Because the Stoney formula is commonly used to relate stress to curvature for thin coatings, a new calculation formula was developed to estimate the residual stresses of thick coatings that represent a comprehensive stress state of the coated specimen. Based on the deduced formula and accurate curvature measurements, the residual stresses of detonation gun (D-Gun) sprayed WC-Co coatings with different thickness were obtained. With increasing the coating thickness, the residual stress changed gradually from the tensile nature to a compressive nature. Meanwhile, the coating was in an approximately stress-free state at the thickness of around 365 mu m. The analysis results emphasized the significance of peening stress in controlling the final stress state of the coated specimen, due to the high spraying velocity and kinetic energy during the D-Gun spraying process. Finally, the effects of residual stress on the mechanical properties of the coating were understood, namely, the compressive stress could significantly improve the coating properties, whereas the tensile stress impaired the coating properties. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

Study on the effect of multiple laser shock peening on residual stress and microstructural changes in modified 9Cr-1Mo (P91) steel

Abstract: This paper presents an experimental study on the effect of laser shock peening (LSP) parameters on resultant surface residual stress and microstructural evolution in P91 steel. P91 steel samples were subjected to single and multiple LSP treatments. Single LSP treatment was performed with laser power density (LPD) in the range of 3.9–5.5 GW cm−2 while multiple LSP treatment was carried out a fixed LPD of 3.9 GW cm−2. The surface of laser shock peened samples was investigated with respect to residual stress, microstructure and micro-hardness through X-ray diffraction (XRD), scanning and transmission electron microscopy and micro-hardness measurements. Single LSP treatment produced significant increase in the magnitude of compressive residual surface stress (−570 to −610 MPa) with respect to unpeened sample with compressive surface stress of around ±85 MPa. However with increasing the LPD beyond 3.9 GW cm−2, the compressive residual surface stress has marginally increased. On the other hand, in case of multiple LSP treated samples, the magnitude of compressive residual surface stress has been observed at increased depth of 975 μm (double LSP) and ~1200 μm (triple LSP) compared to single LSP impact (~750 μm). Further, microstructural analysis carried out using electron microscopy of laser peened samples demonstrated that in the near surface region, martensite lath structure under gone severe refinement with respect to the unpeened sample having average lath width ~1.2 μm. It has also been noticed that grain refinement is found be more prominent in the case of multiple LSP treated samples. The grain refinement in LSP treated samples was also confirmed by XRD peak broadening which progressively increases with an increase in laser impacts. Electron microscopic characterization revealed that in triple LSP treated P91 samples, well-defined polygonal subgrains of average size ~115 ± 10 nm have been observed at near surface (20 μm depth from top).

Investigation of the influence of incidence angle on the process capability of water cavitation peening

Abstract: Water cavitation peening (WCP), through the cavitation impact induced by the water jet process, has been applied to introduce the compressive residual stress in the surface layer of metallic materials. In the present study, five incidence angles (0°, 30°, 45°, 60°, and 90°) were adopted. The impact pressure induced by the bubble collapse was measured by a pressure measurement technique with pressure sensitive film. The residual stresses of a spring steel SAE 1070 plate specimen treated by WCP were determined through X-ray stress analysis. The results indicated that the impact pressure and residual stress obtained at various incidence angles were almost equal to each other in the effective process area. It implied that the process capability of WCP was almost isotropic. Moreover, such potential of WCP was also applied to a carburizing-quenched helical gear, and the high and uniform compressive residual stress was simultaneously introduced in the surface and bottom of gear tooth. It indicated that, compared with the conventional shot peening and laser shock peening, WCP was more effective to the metallic components with the complicated shape.