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Surface Amorphization in Conductive Materials

#3867


Novel High-Power Nanosecond Current Pulse Technology For Surface Amorphization in Conductive Materials

Tech Area / Field

  • PHY-SSP/Solid State Physics/Physics
  • MAT-SYN/Materials Synthesis and Processing/Materials

Status
3 Approved without Funding

Registration date
15.05.2008

Leading Institute
VNIIEF, Russia, N. Novgorod reg., Sarov

Supporting institutes

  • Togliatti State University, Russia, Samara reg., Togliatti

Collaborators

  • Johns Hopkins Medicine / Medical Science and Engineering Department, USA, MD, Baltimore\nTU Bergakademie Freiberg / Institut für Werkstofftechnik, Germany, Freiburg\nOsaka City University, Japan, Osaka\nKanazawa University, Japan, Kanazawa\nUniversity of Illinois At Urbana-Champaign / Department of Physics / Loomis Laboratory of Physics, USA, IL, Urbana

Project summary

The funding support is requested from the ISTC with regard to the Project aiming at the development of a new technology, which would enhance the performance of metals and alloys after modification of their surface structure affecting greatly such properties as fatigue strength, durability etc. The technology relies on the skin-effect induced by a high-power nano-second electric current pulse passing through conductive axi-symmetric samples, which provides fast surface heating and then cooling. The technology allows significant surface modification of metals as a result of rapid heating and quenching giving rise to micro- nano- and even amorphous surface layer formation.

The following is planned to be fulfilled under the Project:

  1. development the new technique of surface amorphization of conductive axially symmetric samples of different metals;
  2. investigation the structure and surface properties of the samples prior and after the high-current nano-second pulsed treatment.

The project significance is justified in light of broad industrial application of inducing amorphism onto surfaces of different electroconductive parts, in particular axisymmetric ones (e.g. axes, bearing needles ect). Many material physical and mechanical properties depend strongly on the surface state. Apparently, strength, fatigue, wear, corrosion and crack resistance enhance considerably as a result of grain refinement and surface amorphization.

The proposed advanced technology of surface amorphization is supposed to improve the surface properties of conductive axially symmetric articles due to a heat treatment caused by a skin effect ensuring a high uniformity and speed of processing. A simple adjustment of the pulse energy allows considerable variability of heating and cooling rate and, therefore, of the resultant surface properties on demand. Finally, the proposed technology would reduce the production cost owing to the lack of necessity of converting the electric energy into electromagnetic radiation.

The key issues of any manufacturing process are relevant to flexibility, applicability and efficiency. As of today, the available surface treatment processes capable of surface amorphization employ quasi-continuous electromagnetic irradiation with different wavelength ranges, i.e. using optical (laser) and/or high-frequency inductive transducers. Such a processing has obvious disadvantages, namely: the electric energy conversion into electromagnetic radiation occurs with quite low efficiency, while the effectiveness of using electromagnetic radiation for structure modification is not high as well. Similar drawbacks are intrinsic to the surface treatment processes using accelerators of electrons or ions. In particular, the disadvantages of laser-induced amorphization are the equipment complexity, high cost, low rate of treatment and relatively poor uniformity of the resultant surface layer. The considerable non-uniformity of the surface layer structure is usually caused by laser beam scanning the treated surface. Besides, high internal stresses are often formed at the amorphous layer/crystal lattice matrix interface. Similar shortcomings are characteristic of the processes employing electron and ion beam accelerators. Manufacturing flows designed around inductive transducers are inefficient in high frequency ranges (dozens MHz and higher), giving rise to a limited heating rate in the surface layer and insufficient cooling-down rate required for amorphization of a pure metal (~1010 -1012 K/s).

The present Project aims at the development of physical grounds and technological flows of a manufacturing process, which would supply fast (within of 40 ns) surface (1-10 µm in depth) heating of an axisymmetric sample. Besides, a high quenching rate (up to 1010 K/s) will be reached leading to the formation of gradient amorphous, nano- and micro-crystalline surface layers. The cost-effectiveness will be enhanced due to reduction of expensive alloying elements (amorphizers), which might become possible due to extremely high quenching rate in the proposed manufacturing processes. Certainly, the most lucrative applications of the proposed technologies will be: (a) obtaining strengthened surface layers with improved wear- and corrosion–resistance; and (b) designing new materials and covers thanks to surface melting, surface-environment interaction and limited diffusion in the modified surface layer.

The Project participants have recently validated experimentally the principal opportunity to modify the surface of electroconductive objects using a high-current nanosecond pulse generator, load unit housing a sample, pulse transmission line, and nanosecond current and voltage sensors.


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