Silicon carbide ceramics are formed by reaction sintering. The sintering temperature is crucial to the product quality of silicon carbide ceramics.
1) sintering temperature is closely related to the density and mechanical properties of silicon carbide ceramics. Under the experiment condition, the sintering temperature within the range of 2160 ~ 2220 ℃, the relative density of sintered silicon carbide ceramic body is more than 96%, can consult the test temperature range, silicon carbide ceramic production process control temperature.
2) under the condition of experiment, the sintering temperature is 2220 ℃ when the highest density of sintered body, the relative density of 98%; Bending strength is 39913MPa, and 2318GPa of vickers hardness is also the maximum. The relation between bending strength and density is approximately linear. The variation trend of vickers hardness value with temperature is similar to that of bending strength, but the fluctuation range is small.
3) the XRD test results indicate that the XRD scanning line of the sintered body is in good agreement with the spectral line of the raw material powder, indicating that no phase transformation occurs during the sintering process, which is consistent with that of the raw material powder, which is dominated by condensed 2SiC. But 250 ℃ high temperature sintering products a few main line of the larger changes in intensity, estimated that related to grain growth, to be further discussed.
4) SEM images of fracture morphology show that when the sintering temperature is low, the sintered body has more pores and lower density. At the proper sintering temperature, the grain began to grow slightly, and the sintering density was higher. High sintering temperature leads to abnormal grain growth, loose structure and decreased density. For the density and the bending strength and hardness values, the best sintering temperature is consistent, the best temperature point around 2200 ℃.