Refractory metals influence on the properties of Fe-Co-Mo(W) electrolytic alloys

Abstract

Abstract The influence of electrodeposition modes on the quantitative and phase composition of the ternary alloys Fe-Co-Mo (W) has been established. The application of pulsed electrolysis provides increasing molybdenum (tungsten) content up to 15–20\xa0at%, at current efficiency of 70–75\xa0%. The analysis of the refractory metals distribution over the coating thickness indicates an increase in molybdenum and decrease in tungsten content with an increase in the electrolysis time. The content of alloying metals in the growing deposits was simulated. The globular developed surface of Fe-Co-Mo(W) coatings is caused by refractory metals incorporation. The results of X-ray diffraction analysis indicate the amorphous-crystalline structure of alloys and intermetallic phases of Fe7Mo, Fe7Co, FeCo, Co7W6, Fe7W6 along with α-Fe and Fe3C. The coherent-scattering region size of the amorphous part is 2–8\xa0nm. The magnetic characteristics of amorphous Fe-Co-W coatings have been established to be depending on deposition time. The conclusion, that the content of magnetic phase in upper layers of coating is greater than in the bottom ones due to decreasing tungsten concentration has been made. The Fe-Co-Mo coatings have been shown to be soft magnetic due to the presence of ferromagnetic phases in the surface layers. The microhardness of ternary coatings deposited in the pulsed mode exceeds the characteristics of ones obtained by direct current and is not inferior to the coatings with hard chromium.