molybdenum silicides

In this study, an attempt was made to synthesize Mo-Si-B multiphase alloy coatings using a combination of mechanical alloying (MA) and air plasma spraying (APS). Mo-14Si-10B (at%) elemental powders were milled using an attritor mill. Mechanically alloyed (MAed) powders as compacted buttons were annealed in an atmosphere controlled furnace at 1100ºC for different times. The annealed Mo–Si–B buttons were crushed, sieved and prepared for coating. Then, powders of Mo-Si-B as alloyed and agglomerated, were plasma sprayed under different conditions onto plain carbon steel. Metallurgical characteristics of powders and coatings were evaluated by SEM, OM, XRD and AAS. The results did not show any related intermetallics after MA. However, Molybdenum silicides were identified when the MAed powders were subjected to high temperature annealing over 10 h. Also, the critical parameters in APS to maintain the starting stoichiometry were identified; this included thermal spraying in an inert environment to minimize the oxidation of coatings. No intermetallic compounds could be identified when alloyed powders were sprayed.