Material removal mechanism of brittle-ductile transition in milling SiC ceramic and experimental verification.

SiC ceramic materials are extremely hard and brittle materials, and are prone to defects such as cracks during processing. It is sensitive to cutting parameters and other processing conditions, making the material extremely difficult to process. This research investigates the material removal mechanism, as well as the influences of cutting parameters and tool wear on the brittle-ductile transition. The relationship between cutting parameters such as feed rate and cutting depth and the ductile–brittle transition was obtained according to the critical load model for brittle material fracture and SiC chip thickness model. Milling tests were conducted, and it was found that with the increase of feed rate and cutting depth, the occurrence of brittle removal increased, and the material removal mode shifted from ductile removal to brittle removal. By the characteristics analysis of force distribution in time–frequency domain, the existence of brittle-ductile transition in SiC milling was proven combined with the analysis of surface roughness and chip morphology. A comprehensive basis for judging the critical transition was provided that the range of parameters is feed rate of 0.015–0.02 mm/z and cutting depth of 0.15–0.2 mm. Tool wear is another significant impact factor on the material removal mode during the milling process. When the tool is worn, it is easier to undergo brittle removal compared to non-worn tools with the same cutting parameters. The brittle-ductile cutting mode of diamond tool milling SiC ceramics and its influence on the cutting force coefficient were also studied based on the milling geometric model. The cutting force mixed with brittle removal and ductile removal is not suitable for identifying the cutting force coefficient. [ABSTRACT FROM AUTHOR]