Manufacturing Nb/Nb₅Si₃ Composite By SHS/QP And Investigating On The Properties

Nb/Nb5Si3 in-situ composites has been considered as high temperature structural materials of high-performance aviation turbine engine because of high melting point, high hardness, high temperature creep strength and lower density. In this paper with Nb、Si powder as the research object, have to explored the ball milling process of the composite powders and study the process of the Nb-Si in-situ composites were fabricated by Self-propagating High-temperature Synthesis plus quick pressing(SHS/QP) technology. The microstructures of the composites were analyzed by scanning electron microscopy(SEM) with electronic differential system(EDS) and X-ray diffraction(XRD). The microstructure and mechanical properties of Nb-Si in-situ composites would be influenced by sintering process parameters.Using the Fourier equation of heat balance, the mathematical model of SHS process in the time of synthesizing Nb/Nb5Si3 in-situ composites under Cr2O3-Al-C combustion system has been established. And on the basis of heat physical analysis, the influence of SHS temperature on SHS volume, relative density were discussed in this paper.The following results have been obtained by the research:1. In this study, two kinds of time varying curve by sintering temperature of composite materials and simulation is compared, the trend similarity and two of the maximum temperature are greater than 1800 K, which indicated the effect of simulation of temperature field is obvious.2. With the preparation of powders,with non-vacuum ball-milling, vacuum ball-milling with 250r/min and 300r/min are measured. Results show that non-vacuum ball-milling leads to serious oxidation in composite powder, vacuum ball-milling with 300r/min show that intermetallic silicides was generated by the reaction between the composite powders and there was no reaction and oxidation between powder under vacuum ball-milling with 300r/min, respectively. Only Si and Nb phase exists after ball milling.3. As to bulk fabrication, Self-propagating High-temperature Synthesis plus quick pressing(SHS/QP) is mainly used, which is an energy efficient way for composites preparation combing SHS and dynamic consolidation to fabricate full-density composites in a single processing operation. The influence under the process parameters(SHS weight, pressure system) on microstructure, performance and relative density were discussed in this paper. It’s demonstrated that with the increase of the SHS weight, the trend was to increase later decrease of the density and hardness of Nb-20 Si bulk material; with the applied pressure, the same trend was to increase later decrease of the density and hardness of the bulk material. The dense bulk with 92.45% relative density and 1615.35 HV was obtained in 300 g SHS system at the pressure of 100 MPa.