Characterization and mechanism of porous silicon carbide ceramics processed by high temperature chemical corrosion

The influence of the process parameters of SiC ceramics on the processing quality was discussed. The corrosion mechanism of SiC ceramics was analyzed. The corrosion rate and porosity of samples were measured by the method of weight-loss and Archimedes respectively. The surface morphology and structure of the specimen were characterized by XRD, SEM and roughness tester. The results show that the corrosion rate increases with the increase of temperature and KOH concentration, and the corrosion effect is significantly improved when the temperature is higher than the boiling point of the alkali solution. The high concentration of alkali solution causes the porosity to decrease, and the increase of temperature can slow down the decrease of porosity. Under the optimized process parameters, the high temperature chemical corrosion can reduce the roughness of the sample, and the minimum roughness(Ra) of the surface is 1.6 μm. The surface quality is improved, the length of contour support is increased, and Rmr (50%) reaches 89.70%. The excessive corrosion temperature or too long time causes the grains to fall off, resulting in a sharp drop of surface quality. In addition, compared with the machining samples, no cracks are found on the sample of high temperature chemical processing. After simple cleaning, the surface has no reactant residue.