Preliminary study on atmospheric-pressure plasma-based chemical dry figuring and finishing of reaction-sintered silicon carbide

Xinmin Shen,Kang Peng,Kazuya Yamamura,Xiaonan Zhang,Hui Deng

doi:10.1117/1.oe.55.10.105102

Abstract

Reaction-sintered silicon carbide (RS-SiC) is a research focus in the field of optical manufacturing. Atmospheric-pressure plasma-based chemical dry figuring and finishing, which consist of plasma chemical vaporization machining (PCVM) and plasma-assisted polishing (PAP), were applied to improve material removal rate (MRR) in rapid figuring and ameliorate surface quality in fine finishing. Through observing the processed RS-SiC sample in PCVM by scanning white-light interferometer (SWLI), the calculated peak-MRR and volume-MRR were 0.533 μm/min and 2.78×10−3 mm3/min, respectively. The comparisons of surface roughness and morphology of the RS-SiC samples before and after PCVM were obtained by the scanning electron microscope and atomic force microscope. It could be found that the processed RS-SiC surface was deteriorated with surface roughness rms 382.116 nm. The evaluations of surface quality of the processed RS-SiC sample in PAP corresponding to different collocations of autorotation speed and revolution speed were obtained by SWLI measurement. The optimal surface roughness rms of the processed RS-SiC sample in PAP was 2.186 nm. There were no subsurface damages, scratches, or residual stresses on the processed sample in PAP. The results indicate that parameters in PAP should be strictly selected, and the optimal parameters can simultaneously obtain high MRR and smooth surface.

Highlights

Reaction-sintered silicon carbide (RS-SiC) ceramic is a promising optical material because of its excellent mechanical, chemical, thermal, and electrical properties,[1,2] which makes it a research focus in the field of optical machining
Plasma chemical vaporization machining (PCVM) is a noncontact figuring technique and the material removal is conducted by chemical reaction, so we suppose that there will be no subsurface damage or residual stresses on the processed sample, which are common in the processed RS-SiC sample obtained by the present mechanical material removal methods
The combination of PCVM and plasma-assisted polishing (PAP) was conducted to verify the feasibility of these techniques for processing an RS-SiC substrate, which was aimed to improve the material removal rate (MRR) in rapid figuring and ameliorate the surface quality in fine finishing

Summary

Introduction

Reaction-sintered silicon carbide (RS-SiC) ceramic is a promising optical material because of its excellent mechanical, chemical, thermal, and electrical properties,[1,2] which makes it a research focus in the field of optical machining. It is difficult to obtain a high material removal rate (MRR) in figuring RS-SiC for its high mechanical hardness and strong chemical inertness.[3,4] What is more, the fabrication process of RS-SiC generates SiC and Si domains in the RS-SiC substrate, and the asymmetric components make it difficult to obtain a high surface quality in the fine finishing of RS-SiC.[5,6] Along with the increasing demands of RS-SiC products with high quality, it is urgently required to develop unique processing techniques. Many techniques have been developed to process this traditional difficult-to-machine material, but few of them can simultaneously obtain high MRR and fine surface quality in machining RS-SiC.[7] An efficient way is the combination of a rapid figuring method and a fine finishing method. PAP was applied to improve the surface quality of the processed RS-SiC sample in PCVM, and the surface roughnesses corresponding to different polishing parameters were obtained by SWLI measurements. By the investigation on MRR in PCVM and the study on surface quality in PAP, the feasibility of these techniques was verified

Experimental Apparatus

Results and Discussion

Conclusions