Mo-14Si-10B, Mo-57Si-10B and Mo-47Si-23B (at%) elemental powders were separately milled using an attritor mill. Mechanically alloyed (MAed) powders were annealed in an atmosphere controlled furnace. Agglomeration process was done for suitably of grain size of composite powders with ultra fine microstructures for using in thermal spraying process. The powders of Mo-Si-B as alloyed (with composites) and agglomerated (without composites) were plasma sprayed onto the surface of plain carbon steel and nickel. Metallurgical characteristics of MAed and/or annealed powders and coatings were evaluated by AAS, SEM, TEM, OM, XRD, TG (DTA) and LPSA. Both coated and uncoated samples were subjected to isothermal oxidation tests and reciprocating wear tests. The results did not show any formation of related intermetallics after MA. However, MoSi 2 , Mo 5 Si 3 , Mo 5 SiB 2 , MoB and Mo were successfully formed, when the MAed Mo-57Si-10B powders were subjected to annealing at a high temperature. Plasma-sprayed Mo-Si-B coatings (without any phases) did not significantly improve the oxidation rate of substrates, but they are excellent to raise the wear resistance of samples. On the other hand, plasma-sprayed Mo-Si-B coatings greatly improve the oxidation resistance of the substrates, but they have no important influence on wear resistance. Key Words Molybdenum silicides, Mo-Si-B, Phase identification, Mechanical alloying, Air plasma spraying. Introduction Mechanical alloying (MA) technique is an important method in powder metallurgy because of its high flexibility, simple control of process parameters and ability to produce a wide spectrum of materials [1]. During the past decade considerable research has been focused on ultra-high temperature structural materials as a potential candidate to replace Ni-based superalloys in turbine engines for efficiency improvement and thrust increment [2]. Mo-based composites are one of
