Developments in Ceramic Materials Research

48
Z. C. Li, Z. J. Pei and C. Treadwell
5. RUM OF CERAMIC MATRIX COMPOSITES
Ceramic matrix composites (CMC) combine reinforcing ceramic phases with a ceramic
matrix to create materials with superior properties (like high-temperature stability, high
thermal-shock resistance, and lightweight), providing unique engineering solutions
[Richerson, 1997]. The combination of these characteristics makes CMC an attractive
alternative to traditional materials such as high alloy steels and refractory metals [Richerson,
1997; Okamura, 1995; Freitag and Richerson, 1998]. Benefits of using CMC include
increased energy efficiency, increased productivity, and regulatory compliance. CMC have
been used in some areas for years, such as cutting tools and wear parts [Anonymous, 2000].
Other emerging applications being field-tested or in the development stage include gas
turbine seals, hot gas filters and high-pressure heat exchangers [Anonymous, 2000].
Currently, a major obstacle to broad applications of CMC is that the CMC materials,
especially those with continuous reinforcements, generally require more costly manufacturing
processes [Freitag and Richerson, 1998].
5.1. Effects of Process Parameters on Cutting Force
The cutting force shows a significant undulation when machining CMC using RUM. This
is due to the fiber lamellar structure and some hard inclusions in the CMC materials. These
two characteristics of CMC make it difficult to estimate main and interaction effects for the
maximum cutting forces. Therefore, the average cutting forces instead of the maximum
cutting forces are used for analysis in RUM of CMC materials.
The average cutting force increases with the increase of feedrate as shown in Figure 17.
This trend is consistent with that when RUM of alumina [Jiao et al., 2005] and when RUM of
Silicon carbide [Churi et al., 2007].
Figure 17. Effect on cutting force in RUM of CMC (after [Li et al., 2006]).