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To decrease the turning-induced pitting susceptibility of laser-cladded Fe–Cr–Ni layer by low plasticity burnishing

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Zhang P. , Hu S. , Lv T. , Du J. , Su G. , Liu Z. , Xu C.

Archives of Civil and Mechanical Engineering

2022

tom Vol. 22, no. 4

art. no. e179, 2022

Corrosion resistance of machined surface and its correlation with surface roughness have been the important concerns for sustainability of the final products. However, the pitting corrosion of laser-cladded Fe–Cr–Ni layers by turning exhibits susceptibility to surface roughness characteristics. In present study, the generation mechanism of pitting susceptibility by turning and the effect of burnishing on decreasing the pitting susceptibility were explored. To this end, a theoretical model of the potential difference between roughness peaks and valleys was established with considering the functional parameters of the surface roughness. Then, the correlations between the potential difference and pitting characteristics including pitting depth, width and area were analyzed in order to reveal the generation mechanism of pitting susceptibility. The occurrence of pitting corrosion could be predicted by the local potential difference, which was higher at the location where pitting corrosion would occur while lower where pitting corrosion did not occur. Finally, the influence of each functional parameter of surface roughness on the potential difference was analyzed using the proposed model, with which the machining schematics were discussed. On the basis of this research, it was expected to improve the corrosion resistance of the claddings by turning and subsequent burnishing process chain.

New approach towards the machining process after laser cladding

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Shen X. , Su H. , Wang J. , Zhang C. , Xu C. , Bai X.

Archives of Civil and Mechanical Engineering

2021

tom Vol. 21, no. 1

136--152

As a chip-free and high-efficiency three-dimensional forming technology, laser cladding has been successfully applied in the green manufacturing and remanufacturing of some high-end engineering parts/components. However, in most cases, cladding coatings need to be machined due to the poor surface finishing by sole laser cladding technique. The study aims to explore an effective way to replace the current machining process after laser cladding, which is supposed to be incapable of satisfying the various technical requirements of some high-demand engineering parts/components. With this purpose, three new surface strengthening processes, i.e. ultrasonic roller burnishing at ambient temperature (URB), ultrasonic roller burnishing at warm temperature (UWB), and UWB coupled with continuous heat treatment (UWB/HT), were proposed and comparatively explored. The contact stresses between the contact pairs in URB were calculated and analyzed in theory. A set of ultrasonic roller burnishing equipment was self-manufactured to perform the experiment. Comparing with the conventional process, the three new processes were evaluated mainly from aspects of surface finishing, the adhesion behavior and corrosion resistance of the finished surface. Summarily, ultrasonic warm burnishing coupled with continuous heat treatment (UWB/HT) is considered to have the greatest potential to achieve the effective machining after laser cladding with excellent surface finishing over the other two strategies, which is expected to further advance the application of laser cladding technique particularly in the fabrication of some high-demand products serving in harsh conditions.

Surface properties enhancement of Inconel 718 alloy by ultrasonic roller burnishing coupled with heat treatment

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Shen X. , Gong X. , Wang B. , He J. , Xu C. , Su G.

Archives of Civil and Mechanical Engineering

2021

tom Vol. 21, no. 3

618--634

Ultrasonic burnishing (UB), in which a ball tip is usually utilized, has been proved to be an effective method for metal surface strengthening. In this study, a roller tip was employed in the ultrasonic burnishing of Inconel 718 alloy (ultrasonic roller burnishing, URB). Meanwhile, a new surface modification technique, i.e., a combination of URB and heat treatment (URB/HT), was advanced to achieve better surface finishing. The surface integrities together with the mechanical behaviors of various samples treated by URB or URB/HT were experimentally examined and compared. Meanwhile, the transient stress distribution of the being treated materials with two treatments was comparatively analyzed by the FEA method. As result, compared with URB, the URB/HT-treated sample had better surface morphology, lower surface roughness, higher micro-hardness, and more well-distributed compressive residual stress. Furthermore, URB/HT-treated samples presented higher yield strength and lower wear rate in comparison with the URB-treated ones. The reduction of deformation resistance and easy flow of the near-surface material during URB/HT treatment mostly contributed to the excellent surface finishing.