Study On The Fabrication And Its Properties Of The MoSi₂(p)/RBSC Composite

With the excellent properties and its low cost ,the RBSC materials was widely applied . But usually ,the RBSC materials contains some amounts of free silicon .The existence of the free Si limits its summit use temperature . An ideal way to improve this is to replace the free Si with MSi2 (M stands for metal element )with a melting point up 1700 1C.A composite of MoSi2 (p)/RBSC was fabricated by the infiltration of the Si-Mo alloy infiltrant into the performs . The free Si was partly replaced with the MoSi2 particles .distributed between the SiC particles. The sintering process was detailed discussed in the paper .It shows with the increase of the amount of the Mo in the Si-Mo infiltrant ,the density of the infiltrated materials with the same performs increased ,but the amount of the free carbon and pore also increased .It was the result of the capillary chocking-off caused by the separation of the MoSJ2 from the alloy infiltrant during the sintering process .After th thermal treatment at 2050,the amount of the free carbon and pore decreased .Also .another cause for the unfully conversion of C into SiC was the gas pressure .larger than the capillary force. The gas is the products of the reaction between the C and the impurities and some other impurities which volatilize at high temperature .Because of the free C and pore .the strength of the infiltrated materials was lower than that of the RBSC materials.A model was established to estimate the volume fraction of the reaction products against the change of the initial pore volume fraction of the perform. It shows there was a critical volume fraction .Only when the initial pore volume fraction of the perform equal to the critical volume fraction, the free Si was fully replaced with the MoSi2 particles.Otherwise .there would be free C and free Si in the infiltrated materials.On the other hand .the composite of MoSi2 (p)/RBSC was also fabricated by the infiltration of the Si into the performs which consists of C and MoO3.The MoSi2 particles were uniformly distributed .It shows .the properties of the infiltrated materials are not in line with the amount of the MoO3 of the perform.. There was an optimum value for the the MoO3 of the perform. When the initial SiC particles with small size were added into the performs, the properties of the infiltrated were improved. The effect of the MoO3 particles on the sintering process was detailed discussed in the paper.