Development of sealing compositions with nanostructure iron-based fillers

Abstract

621.762The possibility of utilizing nanopowders of iron and Fe − Co − Ni produced bu a thermochemical method in the fabrication of sealing composition materials is investigated. It is established that such hermetic sealing composition materials function reliably under extremal conditions and guarantee elevated strength of adhesion to the surface of the metal and high corrosion and temperature stability.There is a need today for new methods of fabricating and investigating the properties of nanostructure sealing composition materials as well as improving existing methods. Of particular note in this connection is the regulation of the thermal and chemical stability of the structures that are obtained as well as questions related to the reliability and service life of these composite materials on objects that are to be protected against damage. The efficiency and reliability of a sealing composition material are determined largely by its ability to withstand extremal conditions caused by the external environment and repeated thermocycling in the interval of temperatures from −50 to +50°C. The composite material must possess high corrosion resistance and increased strength of their adhesion with metal.In the course of use (for example, in pipelines), maintenance operations, in particular, to eliminate leakage of gas out of discontinuities (air holes, cracks, microcracks, and other flaws), represent a special difficulty. Such operations are basically carried out through the use of welding, vibratory treatment of welded structures, and ultrasonic impact treatment. In practice, however, these techniques are not always implemented. In such cases the use of sealing compositions (sealants), which function for lengthy periods of time under rigid conditions without the need for additional bonding or preliminary treatment of the bonded surfaces [1], is an extremely promising approach.Therefore, the objective of the present study is to investigate the use of ferromagnetic powder as a nanostructural component in creating sealing compositions that function under extremal conditions (in the interval of temperatures from −50 to +50°C and at a pressure of 6.5 MPa). Analysis of known data and preliminary trials showed that other fillers do not always conform with the requirements imposed on the composite materials that are used to create hermetic sealing of cracks in gas pipelines [2]. Thus, the principal drawbacks with the use of, for example, powders of electrolytic or carbonyl iron as filler for composite material can be seen in their pyrophoricity and corrosion instability at temperatures from −50 to +50°C, the hydrophobicity of the surface (nonwettability of particles by the solvent), and the impossibility of assuring homogeneity of the composition (particle size 1-5 μm).The use of iron oxides with hydrophobic surface of particles as filler similarly does not enable us to produce a composite material capable of functioning under extremal conditions. In certain cases such filling is possible but to assure that the composite mate...