Electroless Coating of Permalloy Powder and DC-resistivity of Alloy Composites

A. OZOLS, M. PAGNOLA, D. IÑAKI GARCÍA Y H. SIRKIN

SURFACE AND COATINGS TECHNOLOGY

Elsevier B.V

Año: 2006 vol. 200 p. 6821 - 6825

0257-8972

A high resistivity coating of Permalloy (Ni-17.81Fe-1.97Mo wt-%) powders for soft magnetic composites, SMC, manufacturing was developed and characterized. The coating was based on electroless plating method employed an aqueous solution of sodium and nickel phosphate. The chemical process led to a formation of layer up to 1 mm thick deposited on each particle surface and composed by mixture of Ni(OH)2, P2O5 and NaPO3 compounds, according to X ray photoelectron spectrometry and X ray powder diffraction studies. The effect of coating on electrical DC resistivity was evaluated on SMC obtained mixing the metal, coated or uncoated, and thermoplastic polymer (PEEK (Polyetheretherketone) powders, pressing the mixture at 800 MPa and heating in air up to melting the polymer (380-410 ºC). The SMC made with coated powders shown a raise of resistivity more than two orders of magnitude than the obtained with uncoated powders when the polymer ranged 0.5-1.5 wt%. This difference prevails in comparison with sintered materials processed by pressing at same pressure and sintering in hydrogen at 1350ºC. Thus, this process could restrict the Eddy Currents which affect the soft magnetic powder metallurgy product performance for AC applications.