Relating residual stresses to machining and finishing in silicon carbide

Abstract

Machining and surface finishing is essential in the processing of many ceramics, however, it can be detrimental to subsequent performance as it introduces residual stresses and structural defects. Using micro-Raman spectroscopy the residual stress and crystallinity of hotpressed SiC tiles was examined after finishing with several different methods. 514 nm and 633 nm lasers in both conventional and confocal settings enabled stress as a function of depth to be assessed. Single crystal, electronics grade SiC was used for comparison. Compressive residual stresses were present at the surface and in the sub-surface region in all the samples, but the surface with lowest roughness and a mirror-like finish had the highest residual stress. Crystallinity in SiC is reduced by defects and stacking faults produced during machining and finishing. The finer surface finishes had higher residual stresses, but were actually found to have better crystallinity than the rough surfaces. The dependence of residual stress and crystallinity on surface roughness is attributed to a change in the mode of ceramic removal from energetic and brittle for rough finishes to ductile for the shallow cuts of smooth finishes. The dependence of stress and crystallinity on roughness means a balance must be struck between smoothness, crystallinity and stresses in choosing the best finish for a given application.

Influence of the fiber orientation on 3D C/C–SiC composite material and its formation mechanism of the machining surface

“…To maintain the surface shape stability and ameliorate the mechanical properties of the workpiece material, hence, there is certainly need to effectively characterize and eliminate the additional residual stress with appropriate technique. At present, there are many reports on grinding residual stress and its elimination process and studies of the residual stress on the ground surface of SiC materials [34][35][36], but few reports on the characterization and elimination of residual stress for the ground surface of C/C-SiC composite material. In addition, the investigation on the machining of C/C-SiC composite material is mainly focused on unidirectional or 2D C/C-SiC composite.…”

Study of the Effect of Curing Residual Stress on the Bonding Strength of the Single Lap Joint Using a High-Temperature Phosphate Adhesive

“…Ample research has been performed on the residual stress in bonding structures [ 5 , 6 , 7 , 8 ]. Xiao et al found that residual stress could be reduced by starting the bonding while avoiding the corner of the path, turning the laser off gradually and heating the glass substrates [ 9 ].…”

Investigation on Indentation Cracking-Based Approaches for Residual Stress Evaluation

“…RS can also enhance the mobility of charge carriers in semiconductor devices [ 2 ]. Hence, RS play a central role regarding the performance of brittle structures, and their determination has been of considerable interest [ 3 , 4 ].…”