Abstract
In recent years, reaction-sintered silicon carbide (RS-SiC) has been of interest in many engineering fields because of its excellent properties, such as its light weight, high rigidity, high heat conductance and low coefficient of thermal expansion. However, RS-SiC is difficult to machine owing to its high hardness and chemical inertness and because it contains multiple components. To overcome the problem of the poor machinability of RS-SiC in conventional machining, the application of atmospheric-pressure plasma chemical vaporization machining (AP-PCVM) to RS-SiC was proposed. As a highly efficient and damage-free figuring technique, AP-PCVM has been widely applied for the figuring of single-component materials, such as Si, SiC, quartz crystal wafers, and so forth. However, it has not been applied to RS-SiC since it is composed of multiple components. In this study, we investigated the AP-PCVM etching characteristics for RS-SiC by optimizing the gas composition. It was found that the different etching rates of the different components led to a large surface roughness. A smooth surface was obtained by applying the optimum gas composition, for which the etching rate of the Si component was equal to that of the SiC component.
Highlights
In recent years, reaction-sintered silicon carbide (RS-SiC) has been of interest in many engineering fields because of its excellent properties, such as its light weight, high rigidity, high heat conductance and low coefficient of thermal expansion
The reason why the CF4 was ionized at the second time but not ionized directly by the microwave electric field is that the F radicals are very reactive, and would have corroded the ceramic tube, decreasing its lifetime, and contamination due to the precipitation of substances originating from the etched ceramic tube would have interfered with the etching process
It can be observed that the regions between the SiC grains are filled with Si and that many scratches were formed on the surface
Summary
Reaction-sintered silicon carbide (RS-SiC) has been of interest in many engineering fields because of its excellent properties, such as its light weight, high rigidity, high heat conductance and low coefficient of thermal expansion. RS-SiC contains multiple components such as SiC and Si. Owing to the difference in the chemical and mechanical properties of SiC and Si grains, it is difficult to form an objective shape with an ultrasmooth surface. As a highly efficient and damage-free figuring technique, atmospheric-pressure plasma chemical vaporization machining (AP-PCVM) was proposed[14,15]. Since AP-PCVM is a noncontact chemical figuring technique that does not apply a mechanical load to substrates, an SSD layer is not formed in the removal process. In conventional low-pressure plasma processing, the material is etched by the reaction with chemically active radicals formed in a glow discharge, and the entire surface of the sample is exposed to the plasma and modified. The temperature of the surface irradiated by plasma, which was measured by infrared thermography, was less than 50 °C
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