Effect of cladding powder composition on microstructure and mechanical properties of the clads obtained on 304SS using GTAW process One of the most usual processes in surface engineering is cladding of the surface of components. Since the major destruction mechanisms of components are usually begins from the surface, therefore protection and strengthening of their surfaces are vital and crucial issues in determination of the quality and durability of components and consequently the performance of the manufacturing unit and the final cost of products.. For this purpose, in the present study, cladding of the 304 stainless steel by molybdenum and chromium and its effect on the microstructure and hardness of the cladded layer was investigated. In this regard, by simultaneous synthesis of molybdenum from molybdenum trioxide and chromium from chromium oxide, the elements were provided on the clad. The cladding was also performed both with and without the presence of potassium permanganate and carbon. For this purpose, 304 stainless steel specimens were cladded by gas tungsten arc welding method. To do this, powder mixture containing chromium oxide, molybdenum trioxide and nickel with various amounts of potassium permanganate graphite as the source of carbon were prepared with appropriate stoichiometric ratio and milled. Then, the sodium silicate binder was added to the mixture, and the resulting pasty mixture was applied on the surface of the specimens as a pre-placed past. After drying in the air and oven, the cladding was carried out using GTAW. The cross-sections of cladded samples were studied by optical microscopy (OM) and scanning electron microscopy (SEM). The results revealed that microstructure of the weld zone consisted of austenite and ferrite which formed during the solid state transformation of primary ferrite to austenite in the cooling cycle, so that the morphology of ferrite in the center of the weld was lathy ferritic in austenite matrix which changed to skeletal ferrite in the interface of the substrate and clad. It was also found that addition of potassium permanganate to the preset paste layer increased the temperature of weld pool, which enhanced the synthesis of molybdenum and chromium and resulted in the increase in the amount of ferrite in the microstructure of the cladded layer. X-ray diffraction was used to study the phase composition of cladded layers. Presence of the Cr 1.36 Fe 0.52 , FeMo and MoNi 4 peaks in the diffraction patterns of the cladded specimens showed that molybdenum and chromium was synthesized in the weld pool. The microhardness profile of cladded samples demonstrated that the maximum value of hardness in the cladded layers was changed from 230 HV for the sample without potassium permanganate and graphite to 302 HV for the sample contained 3 moles of potassium permanganate and 5 moles of graphite. The value of hardness decreased by increasing the distance from the weld center due to the decrease in the amount of ferrite. Keywords: Synthesis, 304 stainless steel, Lathy ferrite, Skeletal ferrite, Cladding, Gas tungsten arc welding