The conversion of carbon preforms to dense SiC by liquid infiltration is a prospectively low-cost and reliable method of forming SiC-Si composites with complex shapes and high densities. Si powder was coated on top of a 2.0wt .% Y₂O₃-added carbon preform, and reaction bonded silicon carbide (RBSC) was prepared by infiltrating molten Si at 1,450°C for 1-8 h. Reactive sintering of the Y₂O₃-free carbon preform caused Si to be pushed to one side, thereby forming cracking defects. However, when prepared from the Y₂O₃-added carbon preform, a SiC-Si composite in which Si is homogeneously distributed in the SiC matrix without cracking can be produced. Using the Si + C → SiC reaction at 1,450°C, 3C and 6H SiC phases, crystalline Si, and Y₂O₃ were generated based on XRD analysis, without the appearance of graphite. The RBSC prepared from the Y₂O₃-added carbon preform was densified by increasing the density and decreasing the porosity as the holding time increased at 1,450°C. Dense RBSC, which was reaction sintered at 1,450°C for 4 h from the 2.0wt.% Y₂O₃-added carbon preform, had an apparent porosity of 0.11% and a relative density of 96.8%.

Infiltration is a popular technique used to produce valve seat rings and guides to create dense parts. In order to develop valve seat material with a good thermal conductivity and thermal expansion coefficient, Cu-infiltrated properties of sintered Fe-Co-M(M=Mo,Cr) alloy systems are studied. It is shown that the copper network that forms inside the steel alloy skeleton during infiltration enhances the thermal conductivity and thermal expansion coefficient of the steel alloy composite. The hard phase of the CoMoCr and the network precipitated FeCrC phase are distributed homogeneously as the infiltrated Cu phase increases. The increase in hardness of the alloy composite due to the increase of the Co, Ni, Cr, and Cu contents in Fe matrix by the infiltrated Cu amount increases. Using infiltration, the thermal conductivity and thermal expansion coefficient were increased to 29.5 W/mK and 15.9 um/m°C, respectively, for tempered alloy composite.