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Start Over Author "Liu, Wenjin" Publisher laser institute of america
50 results on '"Liu, Wenjin"'

2. Nanostructural features in nanoporous copper coatings fabricated by laser deposition

Author

Zhang Hongjun, Ma Ming-Xing, Liu Wenjin, Kan Yide, Zhong Minlin, Zhang Weiming, and Kang Rui-Quan

Subjects
Fabrication, Materials science, Nanoporous, Metallurgy, Alloy, chemistry.chemical_element, engineering.material, Microstructure, Copper, chemistry, engineering, Nanoscopic scale, Dissolution, Powder mixture
Abstract

Nanoporous metals are now attracting more and more attention for their novel physical, chemical and mechanical properties. It is of great scientific and engineering significance to deposit nano-structure on macro-component surface to locally achieve nano-properties for potential applications. Laser deposition offers a promising approach to deposit a designed structure with designed composition on any location of a component.Nanoporous copper coatings with nano scale porosities were fabricated in this work by laser deposition and dealloying of copper alloy layer on macro-component surface. The fabrication process is constituted of three steps: 1) laser deposition of a MnxCu1-x powder mixture on steel substrates to obtain layers with exact composition; 2) high speed laser remelting of alloy layers to obtain microstructure refinement and composition homogeneity; 3) electrochemical dealloying of remelted layers to obtain nanoporous structure. Dealloying potential and alloy coatings’ composition take important part in microstructure evolution of nanoporous copper, with great impacts on both size and morphology of the nanoporous structure. Microstructural investigations confirm that there is a critical dealloying potential for nanoporous structure formation. When the potential set to a low level, dissolution of Mn as well as pores evolution is restrained. When the potential set to a high level above the critical, dissolution of Mn gets accelerated resulting in pore coarsening. Moreover, alloy coatings with different chemical compositions result in nanoporous coatings with different microstructures, when dealloyed on their own critical potentials.Nanoporous metals are now attracting more and more attention for their novel physical, chemical and mechanical properties. It is of great scientific and engineering significance to deposit nano-structure on macro-component surface to locally achieve nano-properties for potential applications. Laser deposition offers a promising approach to deposit a designed structure with designed composition on any location of a component.Nanoporous copper coatings with nano scale porosities were fabricated in this work by laser deposition and dealloying of copper alloy layer on macro-component surface. The fabrication process is constituted of three steps: 1) laser deposition of a MnxCu1-x powder mixture on steel substrates to obtain layers with exact composition; 2) high speed laser remelting of alloy layers to obtain microstructure refinement and composition homogeneity; 3) electrochemical dealloying of remelted layers to obtain nanoporous structure. Dealloying potential and alloy coatings’ composition take important...

Published
2008

3. Comparative study of techniques for wear minimisation of engine parts

Author

Stefan Kaierle, Shen Yi, Liu Wenjin, Martin Dahmen, Wu Aiping, and Wang Hequiang

Subjects
Wear resistance, Dead centre, Materials science, Abrasive, Transformation hardening, Piston ring, Field tests, Composite material, Lubricant
Abstract

In order to increase wear resistance investigations of locomotive engine parts on the comparison of different techniques for surface treatment were undertaken and compared with respect to their best fit for purpose. Base of the development was to improve the resistance of cylinder liners against abrasive wear in the region of the upper dead centre as well as of piston ring grooves against wear and deformation. Techniques compared are laser transformation hardening and laser-assisted alloying. During surface characterisation and wear tests alloyed surfaces have shown a better integrity of the surface and slightly smaller abrasion. The break out of Steadite grains observed in the hardened surfaces will increase the capacity of lubricant storage and improve failsafe running functions. This effect makes transformation hardening the preferred technique for cylinder liner treatment. For the piston ring grooves careful analysis has proven the equivalence of the techniques. For reasons of simplicity in production also transformation hardening will be preferred. However, the balance will turn according to the field tests of the components which are currently under appraisal.In order to increase wear resistance investigations of locomotive engine parts on the comparison of different techniques for surface treatment were undertaken and compared with respect to their best fit for purpose. Base of the development was to improve the resistance of cylinder liners against abrasive wear in the region of the upper dead centre as well as of piston ring grooves against wear and deformation. Techniques compared are laser transformation hardening and laser-assisted alloying. During surface characterisation and wear tests alloyed surfaces have shown a better integrity of the surface and slightly smaller abrasion. The break out of Steadite grains observed in the hardened surfaces will increase the capacity of lubricant storage and improve failsafe running functions. This effect makes transformation hardening the preferred technique for cylinder liner treatment. For the piston ring grooves careful analysis has proven the equivalence of the techniques. For reasons of simplicity in production...

Published
2008

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