Preparation Of Yttrium Silicate-Nickel Composite Coating On Pure Iron

Coating techniques aim to optimize the surface property and quality via physical and/or chemical methods so as to enhance the global service behaviors.Up to now,many coating techniques have been developed to realize the surface modification of metallic and/or non-metallic materials,among which combination of different coating techniques has drawn increasing interest.Besides,developing novel coating techniques of simple,cheap and wide applicable is of great important.Concerning that coatings of metallic materials usually faces the serious oxidation at high temperatures and the lower bonding strength,it is keen to develop novel coating technique.Consequently,in the present study,Yttrium Silicate-Nickel composite coatings were proposed to fabricate on the surface of a model pure iron using electrophoresis deposition and electro-deposition techniques.The method and mechanisms responsible for the making yttrium silicate powder were firstly studied.Then,the microstructure of the coating layers was characterized and the influence of the yttrium silicate content were addressed.Finally,the high temperature oxidation resistance,bonding strength and the density of the coating layers were evaluated.The following main conclusions were obtained:（1）High-purity Y₂Si₂O₇and Y₂Si O₅powders were obtained by ultrasonic chemical precipitation,with a powder particle size of less than 2 um;Yttrium silicate-Ni composite coatings with uniform particle distribution were obtained by electrophoretic deposition-electrodeposition,the thickness of the composite coating is～20μm,the yttrium silicate content is～48%and the Ni content is～52%.（2）The influence of different parameters on the content of yttrium silicate content was obtained.The content of yttrium silicate particles in the composite coating is positively correlated with the electrophoretic deposition voltage,electrophoretic suspension concentration and electrophoretic deposition time,but negatively correlated with the electrodeposition cathode current density.（3）High temperature oxidation resistance of pure iron was enhanced by composite coating.Pure iron shows a weak-resistant level of oxidation at 500 and 600℃,and none-resistant at 700℃;the composite coating shows high-resistant level at 500-700℃and sub-resistant level even at 800°C.（4）The composite coating has good density and relatively high bonding strength.The average porosity is 1.1/cm² and the average tensile strength of the entire composite coating is greater than 16.1 N/mm².