Electrodeposition behavior and properties of iron-group metal alloys with W from ammoniacal citrate baths

Electrodeposition behavior of iron-group metal alloys with W was studied in ammoniacal citrate baths of various compositions at 50 degrees C under gal vanostatic conditions. The wear and corrosion resistances of iron-group met al alloys with W were also investigated by sliding wear test of ring-on-pla te type at 300 degrees C and dipping test in HNO3, H2SO4 and HF solutions. The results obtained were as follows: (1) The relationship between the alloy composition and the cathode current efficiency showed the existence of two characteristic alloy compositions, i .e., the one appeared at a maximum partial current efficiency of W and the other corresponded to the limiting W content. (2) Electrodeposition behavior of iron-group metal alloys with W was explai nable by the mechanism that the intermediate W4+ oxide electrochemically fo rmed was reduced by atomic hydrogen held on freshly deposited iron-group me tals. (3) The wear resistance of iron-group metal alloys with W was improved with increasing W content in the deposit and showed the best performance at 30 similar to 40 mass% W. When W content in the deposit was high, hardness of the film was increased to prevent adhesive wear between the film and press ring. Hardening of the film due to the frictional heat also seemed to be co ntributed to the improvement of wear resistance. (4) The corrosion resistances of the films were improved with increasing W content in the deposit, especially in HNO3 solutions.