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Thermite assisted synthesis of ZrB2 and ZrB2-SiC through B4C reduction of ZrO2 and ZrSiO4 in air

Journal of Advanced Ceramics 2017年第2期6卷 139-148页

作者： r.v.krishnarao r.SANKArASUBrAMANIAN Defence Metallurgical research Laboratory Kanchanbagh Hyderabad-500058 India

ZrB2 and ZrB2-SiC powders have been produced by reducing ZrO2 and ZrSiO4 with B4C without using any *** was added to the mixtures of (ZrO2+B4C) and (ZrSiO4+B4C).The reaction has been assisted by a floral thermite packed around the *** introducing elemental Si into (ZrO2+B4C) mixture,composite powders of ZrB2-SiC *** leaching out MgO with suitable HCl water solution,the product was analysed by X-ray diffraction (XrD) and scanning electron microscopy (SEM).The effect of Si,B4C,and Mg on the extent of formation of ZrB2,ZrB2-SiC,and other phases has been *** of nano-sized ZrB2 and ZrB2-SiC composite powders was *** adaptability of the process for bulk production was examined.

关键词： ZrB2 ZrO2 zircon (ZrSiO4) composites synthesis

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ZrB_(2)-SiC based composites for thermal protection by reaction sintering of ZrO_(2)+B_(4)C+Si

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Journal of Advanced Ceramics 2017年第4期6卷 320-329页

作者： r.v.krishnarao v.v.BHANUPrASAD G.MADHUSUDHAN rEDDY Defence Metallurgical research Laboratory KanchanbaghHyderabad-500058India

Synthesis and sintering of ZrB_(2)-SiC based composites have been carried out in a single-step pressureless reaction sintering(PLrS)of ZrO_(2),B_(4)C,and Si.Y_(2)O_(3) and Al_(2)O_(3) were used as sintering *** effect of ratios of ZrO_(2)/B_(4)C,ZrO_(2)/Si,and sintering additives(Y_(2)O_(3) and Al_(2)O_(3)),was studied by sintering at different temperatures between 1500 and 1680℃in argon ***_(2),SiC,and YAG phases were identified in the sintered *** as high as 4.2 g/cm^(3),micro hardness of 12.7 GPa,and flexural strength of 117.6 MPa were obtained for PLrS *** material was also prepared by PLrS for tungsten inert gas(TIG)welding of the ZrB_(2)-SiC based *** shear strength of the weld was 63.5 *** PLrS ZrB_(2)-SiC composites exhibited:(i)resistance to oxidation and thermal shock upon exposure to plasma flame at 2700℃for 600 s,(ii)thermal protection for Cf-SiC composites upon exposure to oxy-propane flame at 2300℃for 600 s.

关键词： ZrB_(2) SiC reactive sintering synthesis composites

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Joining and machining of(ZrB2-SiC)and(Cf-SiC)based composites

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Defence Technology（防务技术） 2018年第5期14卷 385-395页

作者： r.v.krishnarao G.Madhusudan reddy v.v.Bhanuprasad Defence Metallurgical research Laboratory KanchanbaghHyderabad500058India

Filler materials of(ZrB_2-SiC-B_4C-YAG) composite were developed for gas tungsten arc welding(GTAW) of the ZrB_2-SiC and Cf-SiC based composites to themselves and to each other. reaction with filler material,porosity and cracks were not observed at weld interfaces of all the joints. Penetration of filler material in to voids and pores existing in the Cf-SiC composites was observed. Average shear strength of 25.7 MPa was achieved for joints of Cf-SiC composites. By incorporation of Cf-SiC(CvD) ground short fibre reinforcement the(ZrB_2-SiC-B_4C-YAG) composite was machinable with tungsten carbide tool. The joint and machined composites were resistance to oxidation and thermal shock when exposed to the oxy-propane flame at 2300℃ for 300s. The combination of(ZrB_2-SiC-B_4C-YAG) and Cf-SiC based composites can be used for making parts like thermal protection system or nozzles for high temperature applications.

关键词： ZrB2-SiC Composite Sintering Machining Gas tungsten arc welding

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Gas tungsten arc welding of ZrB_2-SiC based ultra high temperature ceramic composites

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Defence Technology（防务技术） 2015年第3期11卷 188-196页

作者： r.v.krishnarao G.MADHUSUDHAN rEDDY Defence Metallurgical research Laboratory

The difficulty in fabricating the large size or complex shape limits the application of ZrB2-SiC composites. Joining them by fusion welding without or with preheating, controlled cooling under protective gas shield leads to thermal shock failure or porosity at the weld interface. In the present work, a filler material of(ZrB2-SiC-B4C-YAG) composite with oxidation resistance and thermal shock resistance was produced in the form of welding wire. Using the filler, gas tungsten arc welding(GTAW) was performed without employing preheating, post controlled cooling and extraneous protective gas shield to join hot pressed ZrB2-SiC(ZS), and pressureless sintered ZrB2-SiC-B4C-YAG(ZSBY) composites to themselves. The fusion welding resulted in cracking and non-uniform joining without any filler material. The weld interfaces of the composites were very clean and coherent. The vickers micro-hardness across the weld interface was found to increase due to the increase in the volume % of both SiC and B4C in the filler material. The shear strength of the weld was about 50% of the flextural strength of the parent composite.

关键词：陶瓷基复合材料焊接界面钨极氩弧焊气体保护超高温填充材料 ZrB2 形状复杂

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