Abstract
A composite of (Mo0.9Cr0.1)Si2+15vol% ZrO2 was prepared with powder metallurgy and pres-sure-less sintering, aiming at applications of high temperature structural materials. Mechanical properties of the composites were assessed with hardness, fracture toughness Kc and KIC tested using indentation fracture and SEVNB methods, flexure strength at room temperature and 1200˚C, and isothermal oxidation at 1400˚C. The results showed that the native silica oxide on the silicide feedstock surface, and in turn, the SiO2 in the sintered bulks was significantly re-duced in terms of Cr-alloying. (Mo0.9Cr0.1)Si2 and (Mo0.9Cr0.1)Si2+15vol% ZrO2 composite exhib-ited enhanced sinterability, owing to the formation of (Cr, Mo)5Si3. Fracture toughness of the composite was increased by a factor of 1.6 of that of the monolithic silicide. Mechanical prop-erty of the composite was not affected by Cr addition. However, the high temperature oxidation resistance was greatly improved in the (Mo0.9Cr0.1)Si2+15vol%ZrO2 composite compared with the as-sintered MoSi2+15vol%ZrO2. The Cr-alloying effects on feedstock native oxides, micro-structure, mechanical property and high temperature oxidation resistance were discussed.
Highlights
Molybdenum disilicide MoSi2 is a candidate for high-temperature structural materials due to high melting point, high specific strength, high thermal conductivity, and excellent oxidation resistance at elevated temperature [1]
Significant increasing in fracture toughness and strengthening at high temperature has been reported in MoSi2-ZrO2 composites in terms of phase transformation toughening of ZrO2, but the degraded oxidation resistance was observed, especially with a high ZrO2 content [3] [4]
The purpose of this study is to investigate the alloying effect of Cr addition on mechanical properties and high temperature oxidation resistance in comparison with the un-alloyed MoSi2 + 15vol%ZrO2 composite
Summary
Molybdenum disilicide MoSi2 is a candidate for high-temperature structural materials due to high melting point, high specific strength (strength/density), high thermal conductivity, and excellent oxidation resistance at elevated temperature [1]. (2016) Property and Oxidation Behaviours of (Mo,Cr)Si2 + ZrO2 Composite Produced by Pressure-Less Sintering. Significant increasing in fracture toughness and strengthening at high temperature has been reported in MoSi2-ZrO2 composites in terms of phase transformation toughening of ZrO2, but the degraded oxidation resistance was observed, especially with a high ZrO2 content [3] [4]. In this investigation, Cr alloyed molybdenum disilicide (Mo0.9Cr0.1)Si2, and composite (Mo0.9Cr0.1)Si2 + 15vol%ZrO2 were produced with Pressure-Less Sintering (PLS) that was the most economic and practical technique applied popularly in industrial production. The purpose of this study is to investigate the alloying effect of Cr addition on mechanical properties and high temperature oxidation resistance in comparison with the un-alloyed MoSi2 + 15vol%ZrO2 composite
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