Densification, characterization and oxidation studies of (TiCr)B₂ + 20 % MoSi₂

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• 作者：T.S.R.Ch. Murthy ; ^{murthi@barc.gov.in} ; J.K. Sonber ; C. Subramanian ; R.C. Hubli ; N. Krishnamurthy ; A.K. Suri
• 关键词：Pre-alloyed (TiCr)B2 ; Hot hardness ; Fracture toughness ; CTE ; Electrical resistivity ; Oxidation studies
• 刊名：International Journal of Refractory Metals and Hard Materials
• 出版年：2013
• 出版时间：March, 2013
• 年：2013
• 卷：37
• 期：Complete
• 页码：12-28
• 全文大小：3777 K

文摘

This paper presents the results of detailed studies carried out on synthesis of starting materials and densification of (TiCr)B₂ with MoSi₂ as sinter additive by hot pressing. Dense compacts were characterized by measurement of density, hardness, indentation fracture toughness, flexural strength, coefficient of thermal expansion, hot hardness and electrical resistivity. Oxidation studies were investigated up to 1000 ¡ãC and isothermal oxidation kinetics in the temperature range of 750 to 950 ¡ãC. Phase identification and surface morphology analysis of hot pressed and oxidized samples were done using XRD, SEM-EDS and EPMA.

(TiCr)B₂ composite of 4.81 g/cc density was obtained with the addition of 20 % MoSi₂ by hot pressing at 1800 ¡ãC with 35 MPa pressure. Hardness values of composites were close to 27 GPa and fracture toughness was in the range of 3-5 MPa¡¤m^1/2. Coefficient of thermal expansion was measured and found to be in the range of 6.6-7.5 ¡Á 10^? 6 K^? 1 from room temperature to 900 ¡ãC and electrical resistivity of the composite as 2.1, 2.6 and 3.0 ¦Ì¦¸¡¤cm at 25, 500 and 1000 ¡ãC respectively. Observed nature of oxidation was parabolic for all composites. Formation of continuous and thick glassy film was observed with increased proportion of CrB₂ content in the composite. TiO₂, SiO₂ and Cr₂O₃ phases were mainly identified on the oxidized surface, which are responsible for the improved oxidation resistance of this composite.