High-temperature oxidation of Fe-Mo-Si alloys prepared by spark plasma sintering technique

The present study used mechanical milling and Spark Plasma Sintering (SPS) techniques to synthesize the sintered Fe-Mo-Si alloys from ferromolybdenum and ferrosilicon lumps. Three different compositions of ferromolybdenum and ferrosilicon ratio (in at%) as 65:35, 60:40, and 55:45, namely as 6535FMS, 6040FMS, and 5545FMS, respectively, were prepared at 950 °C for 5 min in holding time under a constant compressive load of 9.3 kN. The high-temperature oxidation resistance of the alloys was cyclically studied at 1000 °C for 12 cycles. The results show that the Fe-Mo-Si alloys with differences in ferromolybdenum and ferrosilicon ratio are composed of hexagonal Iron Molybdenum Silicon (hex-IMS) of Fe2-xMoSix (x = 0.66, 0.96, and 1), Mo5Fe3Si2, MoFe2Si2, and SiO2, depending on its composition. The hex-IMS phase with higher Si content is formed with a decrease in the ferromolybdenum and ferrosilicon ratio. The hardness of the alloys also tends to increase, reaching 1330 HV for 5545FMS alloy. In addition, after exposure at 1000 °C for 12 cycles, the 5545FMS alloy exhibits excellent oxidation resistance, forming duplex oxide scales: Fe2O3 in the outer layer and SiO2 at the outer/alloy interface. Meanwhile, the 6535FMS alloy with higher ferromolybdenum content experienced accelerated oxidation since the initial oxidation stage. The results obtained are presented and discussed in detail in this paper. •Fe-Mo-Si alloys were synthesized from ferromolybdenum and ferrosilicon lumps using mechanical milling and SPS techniques.•Fe-Mo-Si alloys consist of hex-IMS of Fe2-xMoSix (x = 0.66, 0.96, and 1), Mo5Fe3Si2, MoFe2Si2, and SiO2.•The hex-IMS phase with higher Si content is formed with a decrease in the ferromolybdenum and ferrosilicon ratio.•The hardness of the alloys also tends to increase, reaching 1330 HV for 5545FMS alloy.•5545FMS alloy exhibits excellent oxidation resistance, forming duplex oxide scales of Fe2O3 and SiO2.