Abstract
Silicon carbide fiber reinforced silicon carbide ceramic matrix composite (SiCf/SiC composite) is characterized by a high strength-to-density ratio, high hardness, and high temperature resistance. However, due to the brittleness of the matrix material and the anisotropy of the reinforcing phase, it is a huge challenge for machining of the material. The milling method has advantages of a high material removal rate and applicability to complex surface geometry. However, no published literature on milling of SiCf/SiC composite has been found up to now. In this paper, high-speed milling of SiCf/SiC composites was carried out under dry conditions and cryogenic cooling using liquid nitrogen, respectively. Polycrystalline diamond (PCD) and chemical vapor deposition (CVD) diamond cutting tools were used for the milling work. The cutting performance of the two kinds of tools in high-speed milling of SiCf/SiC composites was studied. Tool failure modes and mechanisms were analyzed. The effects of the cooling approach on tool wear and machined surface quality were also investigated. The experimental results showed that under identical cutting parameters and cooling approaches, the PCD tool yielded better cutting performance in terms of a longer tool life and better surface quality than that of the CVD diamond tool. In dry machining, the failure modes of the CVD diamond tool were a large area of spalling on the rake face, edge chipping and severe tool nose fracture, whereas for the PCD tool, only a small area of spalling around the tool nose took place. Compared to the dry machining, the wear magnitudes of both PCD and CVD diamond tools were decreased in cryogenic machining. Additionally, the surface quality also showed significant improvements. This study indicates that the PCD tool is highly suitable for machining of SiCf/SiC composite, and that the cryogenic method can improve machining efficiency and surface quality.
Highlights
With continuous development in science and technology, the requirements of productmaking in the fields of automobile, aerospace, and others are becoming tougher and tougher
Silicon carbide fiber-reinforced silicon carbide ceramic matrix composite (SiCf/SiC composite) is a kind of composite material which is formed by implanting silicon carbide fibers into a silicon carbide matrix
Even though parts and components made of SiCf/SiC composites could be manufactured with a near net shape forming process, subtractive processes such as cutting and grinding are still needed to remove additional materials
Summary
With continuous development in science and technology, the requirements of productmaking in the fields of automobile, aerospace, and others are becoming tougher and tougher. Conventional machining is still a key process to obtain a high material removal rate and fine surface finish of fiber reinforced SiC ceramic matrix composites. Yin et al [18] investigated the influences of grinding parameters on material removal of SiCf/SiC composites. Machining with cutting edge tools is regarded as a process that can achieve a higher material removal rate, better surface quality and size accuracy compared to grinding [24,25,26,27,28]. Diaz et al [29,30] investigated the material removal mechanism in drilling of SiCf/SiC composites with a diamond-coated twist drill It concluded that the fiber was fractured in a brittle way, and the matrix suffered a plastic-dominated mechanism. Parameter Density (g/cm3) Tensile strength (MPa) Elongation (%) Young’s modulus (GPa) Bending strength (MPa)
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