Effect of High-Temperature-Assisted Ultrasonic Deep Rolling on Microstructure and Tribological Properties of Ni-WC Coatings
24 Feb 2023-Coatings-Vol. 13, Iss: 3, pp 499-499
TL;DR: In this paper , the Ni-WC coatings were treated with different preloading depths (0.20 mm, 0.25 mm, and 0.30 mm), and the microstructure and properties of the coatings are characterized by SEM, EDS, X-ray stress analysis, and micro-Vickers hardness testing.
Abstract: Cermet coatings are post-treated by a new surface microcrystallization technology, namely high-temperature-assisted ultrasonic deep rolling (HT + UDR). The process parameters of ultrasonic deep rolling significantly affect the microstructure and tribological properties of the Ni-WC coatings. In this paper, the samples were treated with different preloading depths (0.20 mm, 0.25 mm, and 0.30 mm), and the microstructure and properties of the coatings were characterized by SEM, EDS, X-ray stress analysis, and micro-Vickers hardness testing. An MMW-1A-type friction and wear tester was used for the dry friction and wear test at room temperature, respectively. Compared with the untreated sample, plastic rheology occurred on the surface of the coatings after HT + UDR, showing a phenomenon of “cutting peaks and filling valleys”. In the treated coatings, visible cracks were eliminated, and the inside of the coating was denser. The surface hard phase was increased as a “skeleton” and embedded with the soft phase, which played a role in strong and tough bonding. After HT + UDR + 0.25 mm treatment, the surface roughness increased by 68%, the microhardness of the surface layer reached a maximum of 726.3 HV0.1, and the residual tensile stress changed from 165.5 MPa to −337.9 MPa, which inhibited the germination and propagation of cracks. HT + UDR improved the wear resistance of the coating in many aspects. The coating after the 0.25 mm preloading depth treatment possessed the smallest friction coefficient and the lowest wear amount, which is 0.04 and 4.5 mg, respectively. The wear form was abrasive wear, and the comprehensive tribological performance is the best.
TL;DR: New concepts and principles of using severe plastic deformation to fabricate bulk nanostructured metals with advanced properties are discussed, with special emphasis on the relationship between microstructural features and properties, as well as the first applications of SPD-produced nanomaterials.
Abstract: Despite rosy prospects, the use of nanostructured metals and alloys as advanced structural and functional materials has remained controversial until recently. Only in recent years has a breakthrough been outlined in this area, associated both with development of new routes for the fabrication of bulk nanostructured materials and with investigation of the fundamental mechanisms that lead to the new properties of these materials. Although a deep understanding of these mechanisms is still a topic of basic research, pilot commercial products for medicine and microdevices are coming within reach of the market. This progress article discusses new concepts and principles of using severe plastic deformation (SPD) to fabricate bulk nanostructured metals with advanced properties. Special emphasis is laid on the relationship between microstructural features and properties, as well as the first applications of SPD-produced nanomaterials.
01 Jul 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a surface mechanical attrition treatment (SMAT) was developed for synthesizing a nanostructured surface layer on metallic materials in order to upgrade the overall properties and performance.
Abstract: In terms of the grain refinement mechanism induced by plastic straining, a novel surface mechanical attrition treatment (SMAT) was developed for synthesizing a nanostructured surface layer on metallic materials in order to upgrade the overall properties and performance. In this paper, the SMAT technique and the microstructure of the SMAT surface layer will be described. The grain refinement mechanism of the surface layer during the SMAT will be analyzed in terms of the microstructure observations in several typical materials. Obvious enhancements in mechanical properties and tribological properties of the nanostructured surface layer in different materials were observed. Further development and prospects will be addressed with respect to the SMAT as well as the performance and technological applications of the engineering materials with the nanostructured surface layer.
08 Sep 2014-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effects of ultrasonic nano-crystal surface modification (UNSM) on residual stresses, microstructure changes and mechanical properties of austenitic stainless steel 304 were investigated.
Abstract: In this study, the effects of Ultrasonic Nano-crystal Surface Modification (UNSM) on residual stresses, microstructure changes and mechanical properties of austenitic stainless steel 304 were investigated. The dynamic impacts induced by UNSM leads to surface nanocrystallization, martensite formation, and the generation of high magnitude of surface compressive residual stresses (−1400 MPa) and hardening. Highly dense deformation twins were generated in material subsurface to a depth of 100 µm. These deformation twins significantly improve material work-hardening capacity by acting both as dislocation blockers and dislocation emission sources. Furthermore, the gradually changing martensite volume fraction ensures strong interfacial strength between the ductile interior and the two nanocrystalline surface layers and thus prevents early necking. The microstructure with two strong surface layers and a compliant interior embedded with dense nanoscale deformation twins and dislocations leads to both high strength and high ductility. The work-hardened surface layers (3.5 times the original hardness) and high magnitude of compressive residual stresses lead to significant improvement in fatigue performance; the fatigue endurance limit was increased by 100 MPa. The results have demonstrated that UNSM is a powerful surface engineering technique that can improve component mechanical properties and performance.
TL;DR: In this article, the importance of shot peening process to obtain nanocrystal surface is presented with an inclusive clarification of actual state of the art, and the available microstructural characteristics of thin layers obtained with different processes are depicted.
Abstract: The importance of application of shot peening process to obtain nanocrystal surface is presented with an inclusive clarification of actual state of the art. Description of different shot peening methods which have proved to be able to create nanocrystallised layers is presented. Then the available microstructural characteristics of nanocrystal thin layers obtained with different processes are depicted. In addition, the influence of the process is reviewed on material behaviour under different loading conditions. On this basis, some possible addresses for future research in this field are drawn and underlined.
TL;DR: In this paper, surface enhancement by low plasticity burnishing (LPB) was used to eliminate or reduce the surface tensile stresses necessary for corrosion fatigue failure in AA7075-T6, without alteration of environment, material or component design.
Abstract: Conventional approaches to mitigate corrosion related failure mechanisms in aircraft usually involve isolation from the corrosive environment via protective coatings, alloy substitution, or modifications in design to reduce stresses. This paper describes an alternate approach employing surface enhancement by low plasticity burnishing (LPB) to eliminate or reduce the surface tensile stresses necessary for corrosion fatigue failure in AA7075-T6, without alteration of environment, material or component design. The restoration of fatigue performance by LPB processing of AA7075-T6 after severe pitting in salt fog was previously described. 1 This paper describes benefits of introducing a deep compressive residual stress by LPB on fatigue strength after salt fog pitting and corrosion fatigue (under active corrosion) performance. Since LPB processing was performed in a conventional CNC machining center, it offers a cost effective and practical alternative to alloy substitution or component re-design as a means of improving the structural integrity of aging aircraft.