New method of Ni/WC and Cu/WC composite coatings formation

Abstract

Ni/WC and Cu/WC composite coatings were obtained in two steps. The first step consists of the inert WC particles deposition from the aqueous solution onto steel surface by means of a micro-pipette and covering by the dilute aqueous Nafion solution. The second step is the electrochemical metal deposition from commercial baths in constant current regimes. As result, compact composite coatings were obtained with the different amounts of WC in the deposit in the entire range between a part of a percent up to a few tenths of the percent. The new two-steps method for the formation of the composite coatings renders a very homogeneous distribution of inert WC particles in the deposit and exactly defined chemical composition in each part of the coating Several advantages of splitting the process into two steps are found: the electrolyte for the metal deposition stays clean, no stirring is necessary and it is possible to deposit homogeneously large particles at desired parts of the surface. It is also possible to form multi-layer composite deposits as well as composite foils.

Kompozitne prevlake nikal-volframkarbid Ni/WC i bakar-volframkarbid Cu/WC dobijene su iz dva stupnja. Prvi stupanj obuhvata nanošenje inertnih čestica volframkarbida (WC) iz vodenog rastvora mikropipetom na čeličnu površinu. Preko nanetih čestica sipan je razblažen vodeni rastvor nafiona. Drugi stupanj predstavlja elektrohemijsko taloženje metala iz komercijalnih elektrolita pri konstantnom strujnom režimu. Kao rezultat dobijene su kompaktne kompozitne prevlake, gde je količinu WC moguće menjati od dela procenta do nekoliko desetina procenata. Korišćenjem dvostepenog formiranja kompozitnih prevlaka dobija se homogena raspodela inertnih čestica u prevlaci i tačno definisan hemijski sastav u svakom delu prevlake. Prednost ovakvog formiranja kompozitnih materijala je velika, jer ne dolazi do prljanja elektrolita za taloženje osnovnog metala, nije potrebno nikakvo mešanje elektrolita, a moguće je ugraditi velike i teške čestice i to na tačno definisanim mestima na površini. Takođe, moguće je formirati i višeslojne kompozitne prevlake, kao i kompozitne folije.