Mechanical attrition and mechanical alloying have been developed as a versatile alternative to other processing routes in preparing nanophase powder materials with a broad range of chemical compositions and atomic structures. This internal refining process results in a reduction of the average grain size to nanometer scales by the creation and self-organization of small-angle and high-angle grain boundaries within the powder particles. Similar observations have been made on heavily worn surfaces. Due to the large shear stresses at the rail/wheel contact area of high speed trains, a transformation of the pearlitic steel to a nanocrystalline state and the dissolution of carbides is observed. As a consequence, the microhardness is increased by a factor of five corresponding to about 12 GPa. This non-equilibrium material favors the development of corrugations causing considerable acoustic noise and the formation of microcracks leading to a steady devastation of the rail as well as the wheel. A comparison is being made between the physical properties of the nanostructured surface layers of the rail, ball milled powder particles and severely plastically deformed bulk samples with identical composition.
Nanostructure formation and mechanical alloying in the wheel / rail contact area of high speed trains in comparison with other synthesis routes
2001
8 Seiten, 32 Quellen
Aufsatz (Konferenz)
Englisch
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