Synthesis of a novel MoSS+Mo5SiB2+Mo5Si3 based Mo–Si–B alloy and its enhanced fracture toughness. (September 2022) - Yang, Tao
Abstract: Mo–Si–B based alloys are promising ultrahigh-temperature structural materials for turbine blades. Different from traditional MoSS (Mo solid solution)+Mo5 SiB2 +Mo3 Si based alloy, present paper focuses on a novel non-equilibrium MoSS + Mo5 SiB2 +Mo5 Si3 based alloy, which shows more potential for excellent comprehensive performance. This alloy was synthesized by SPS (spark plasma sintering) technique using pure Mo and Mo5 SiB2 +Mo5 Si3 powders as raw materials. SEM, EDS, XRD, EPMA, single-edge notched bending and nano-identation tests were used to reveal the formation mechanism of this alloy and evaluate its fracture toughness. The results showed that this MoSS + Mo5 SiB2 +Mo5 Si3 based alloy was composed of MoSS, Mo5 SiB2, Mo5 Si3 and a little Mo3 Si. Mo5 SiB2 +Mo3 Si halos were found around the original Mo5 SiB2 +Mo5 Si3 particles as a result of inter-diffusion between Mo and Mo5 SiB2 +Mo5 Si3 during sintering processes. Compared with traditional cast or reaction sintered MoSS + Mo5 SiB2 +Mo3 Si based alloy with the same composition, this MoSS + Mo5 SiB2 +Mo5 Si3 based alloy showed superior fracture toughness benefiting from its higher MoSS content, larger coarseness of MoSS and lower Si concentration in MoSS . Highlights: A novel non-equilibrium MoSS + T2+T1 based alloy is synthesized. MoSS in present alloy offers outstanding toughening effect. MoSS + T2+T1 based alloy shows excellent room-temperature fracture toughness.