Development of Nanograined Metallic Materials by Bulk and Coating Techniques

Abstract

This paper deals with nanograined metallic materials in the bulk and coating forms, produced by different techniques, namely mechanical alloying, gas reduction, annealing sol‐gel, electroless coating, sputtering etc. Metallic nanograined materials studied include PbTe, Fe2Mo, Ti‐Al‐Graphite/Ni‐P, Zr60Cu20Pd10Al10 and Ni‐P‐X (X=Al2O3‐ZrO2 and Ba‐Zn2‐y CoyFe16O27). In mechanical alloying (MA), fracture and cold welding of the particles play an important role in forming bulk nanograined metallic materials. TiAl, a structural material for space application has been produced by MA an attempt has also been made to improve the mechanical property of TiAl by adding Ni‐P coated graphite powder into TiAl prior to the MA. Only recently it has been established that the oxide powder reduction by H2 gas in a fluidized bed reactor produces nanograined intermetallic material. Fe2Mo having high hardness, used for magnetic head could be produced. PbTe an electronic material has also been produced by this method with good yield. The bulk nanograined metallic materials can also be produced from the amorphous materials by controlling annealing parameters. Such metallic glass materials are developed both in the form of bulk as well as coating. Zr60Cu20Pd10Al10 metallic glass has been produced by controlling the process parameters of annealing. By Electroless technique, nanograined coatings such as Cu, Ag‐graphite, Ni‐P, Ni‐B, Ni‐P composite coatings, etc. could be produced. Amorphous Ni‐P substrate, produced by EL technique, has been used for preparing multilayer nanocoating of Cr followed by Co, by using RF magnetron sputtering. Metallurgical tools used for characterization include XRD, SEM, TEM, EPMA, VSM, DSC, AAS, and so forth.