Melt infiltrated ceramic matrix composite

For this article, the term melt infiltrated ceramic matrix composite (MI-CMC) will refer only to continuous fiber composites whose matrices are formed by molten silicon (or silicon alloy) infiltration into a porous SiC- and/or C-containing preform. GE holds nmnerous patents on the composition and fabrication of these materials, only a few of which are listed in reference 10. Such composites can be made from a variety of constituents and processes. A detailed description of the material variations and processes is also given in reference 1, so only an abbreviated description will be given here. 

THERMOCOUPLE INTERACTIONS DURING TESTING OF MELT INFILTRATED CERAMIC MATRIX COMPOSITES... 

Thermocouple Interactions During Testing of Melt Infiltrated Ceramic Matrix Composites... 

Compared with conventional techniques for fabricating ceramic-matrix composites, such as hot pressing (HP), reactive melt infiltration (RMI) and polymer impregnation and pyrolysis (PIP), CVI techniques have distinct advantages, which can be summarised as follows [8, 9] ... 

Both oxide and non-oxide matrices have been used with SiC reinforcements. Examples include alumina matrix composites fabricated by oxidation of an aluminum melt (DIMOX process) (Newkirk et al., 1986), glass-ceramic matrix composites fabricated by hot pressing (Prewo and Brennan, 1980), SiC matrix composites made by CVI (Stinton et al., 1986), SiC or SiC/Si3N4 matrix composites made by polymer pyrolysis, and SiC-Si matrix composites produced by silicon melt infiltration (Luthra et al., 1993). 

The HiPerComp family of ceramic matrix composites, based on silicon melt infiltration composite technology invented by GE, offer a unique combination of high temperature thermal and mechanical properties that make them highly suited for gas turbine engine... 

As high performance ceramic matrix composite systems, such as Melt Infiltrated (MI) SiC/SiC, are being considered for advanced gas turbine engine applications, the characterization of the material becomes more important. A series of tests were conducted where Pt and Ni sheathed Pt thermocouples were used to monitor temperature for short and long duration fast fracture, fatigue and creep tests. While it is known that Si forms eutectics with Pt and Ni, this was initially not considered an issue. But since Ml SiC/SiC composite achieves much of its performance from the infiltrated phase of Silicon (for high conductivity and low porosity), it was felt that further study of possible interactions of the Si phase has to be considered. 

Melt infiltration into fibrous preforms combined with oxidation of the metal matrix can produce ceramic matrix composites. Since this type of process was developed by Lanxide Corporation, it is called the Lanxide process [49]. For example, a Nicalon SiC fiber and alumina matrix composite was produced as follows [50] stacked fibrics of Nicalon fiber were coated by CVD. The major purposes of the coating were to protect the fiber from aluminum alloys during... 

FATIGUE CHARACTERIZATION OF A MELT-INFILTRATED WOVEN Hl-NIC-S/BN/SIC CERAMIC MATRIX COMPOSITE (CMC) USING A UNIQUE COMBUSTION TEST FACILITY... 

Brennan, Interfacial Characterization of a Slurry-Cast Melt-Infiltrated SiC/SiC Ceramic-Matrix Composite, Acta Materialia, 48 4619-28 (2000). 

Fatigue Characterization of a Melt-Infiltrated Woven HI-NIC-S/BN/SIC Ceramic Matrix Composite (CMC) Using a Unique Combustion Test Facility... 

Ceramic Matrix Composites (CMCs) 11 in the broad category of technical ceramics [I]. Unlike monolithic ceramics where surface and sub-surface flaws are known to be clearly detrimental from a tensile and durability [2] point of view, the effect of defects in CMCs is not as clear. The range of porosity (key defect) foimd in oxide/oxide is 25% [3], melt infiltrated nonoxide CMCs is 2% [3], polymer infiltrations pyrolysis ntm-oxide CMCs is 5% [3] and chemical vapor infiltrated non-oxide CMCs is 12% [4]. The properties vary widely between and wifliin these overall CMC classes. The above percent porosity for these classes of CMCs covers the conventional expectations from fabrication and does not consider local variations or unexpected processing concerns. Within all these systems, there is a range of durability behavior seen (both fatigue and creep). 

The widely used fabrication processes for ceramic matrix composite are chemical vapor infiltration (CVl), pol3mier impregnation and pyrolysis (PIP), and reaction melt infiltration (RMl). All of them can also be utilized to fabricate ultra high temperature ceramic matrix composite. 

Reactive melt infiltration (RMI) has been demonstrated to be an effective fabrication route for C/TiC ceramic matrix composite. Tong et al (Tong et al., 2012d) has fabricated a C/C-TiC composite by infiltrated a porous C/C preform with titanium melt. XRD analysis of the composite indicated that the phases in the composite were carbon and TiC. No detectable titanium peak was found in the XRD patterns. 

Wall, N., Yang, J. M. (2012). Reactive melt infiltration processing of fiber-reinforced ceramic matrix composites. In Bansal, N. P., Boccaccini, A. R. (Eds.), Ceramics and composites processing methods (pp. 351-385). Hoboken, NJ John Wiley Sons, Inc. doi 10.1002/9781118176665.chl0. 

Hilhg, W. B. (1988). Melt infiltration approach to ceramic matrix composite. Journal of the American Ceramic Society, 71, 96—99. doi 10.1111/j.l 151-2916.1988. tb05840.x. 

To address the temperature issues related to excess silicon, all the same constituents in the N24-C system are used for potential N26 CMC generations, but remaining open pores in the CVI SiC matrix are filled by silicon-free ceramics, rather than by melt infiltration of silicon. In particular, for the N26-A CMC system, a SiC-yielding polymer from Starfire Inc. [13] is infiltrated into the matrix porosity at room temperature and then pyrolyzed at temperatures up to 2912°F (1600°C). This polymer infiltration and pyrolysis (PIP) process was repeated a few times until composite porosity was reduced to 14 vol,%, At this point, the total CMC system is then thermally treated at NASA to improve its thermal conductivity and creep-resistance. Thus although more porous than the other CMC systems, the N26-A system has no free silicon in the matrix, thereby allowing long-time structural use at 2600°F... 

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