Brush plated cobalt-molybdenum and cobalt-tungsten alloys for wear resistant applications

Brush plating solutions have been developed that enable sound cobalt alloy coatings containing up to 12% molybdenum or tungsten to be deposited at thicknesses up to 13 μm. The alloy deposits had a very fine grain size but their crystallographic structure could not be determined. The cobalt deposit alone had a mixed cph and fcc structure at room temperature. Evaluation of the wear resistant properties of the cobalt alloys was carried out in the laboratory using a pin and disc technique and a simulated hot forging test. Both tests showed the alloys to have relatively good wear characteristics. Extensive industrial trials have been undertaken to assess the value of these cobalt alloy coatings to enhance the performance of hot forging dies. The results have indicated that die life can be increased by up to 100%