Study On The Removal Mechanism And Grinding Technique Of The PCD Cutting Tools

Polycrystalline Diamond is an ideal cutting tool material with extremely high hardness and wear resistance. Since its first appearance in the early 1970s. the cutting tools made by it have been key roles in the development of modern cutting technology and already widely used in automobile, aviation and wood industries. Nowadays, mechanical grinding with diamond wheel is still the main method to manufacture PCD cutting tools, but it also has some drawbacks such as low removal-rate, relatively low grinding quality, and high cost. etc. Especially the low quality resulted from grinding, has become a barricade to the use of PCD tools in the precision and ultra-precision machining. Aiming to solve these problems, the theories about the crystal structure and fracture behavior of diamond were discussed, and the removal mechanism and grinding technique of PCD cutting tools were studied in this paper, by carefully analyzing the micro morphology of PCD tools' ground surface. The outcomes of this study are helpful for people to understand how PCD is removed and how its grinding settings can be optimized to achieve a better grinding quality.Firstly, a new etching method was used to remove the attachment and catalyst Co on the ground surface of PCD tools, through which the real morphology of PCD was achieved. Then, a series of grinding experiments were conducted, and the micro morphology of the ground surfaces of different specimens was studied. According to their unique generation mechanism, the removal forms of PCD were classified into six categories, including micro cracking, grain boundary cracking, fatigue effect, scoring, sliding and mechanical thermo-chemistry effect. And then, the typical micro morphology, generation reasons and forming conditions for each mechanism were discussed based on their relationship with the grinding parameters. Lastly, taking the removal mechanism as the theory basis, the flank surface's integrity and the cutting edge's serration of different PCD tools were compared, and the influence of the grinding fluid. grinding speed and grinding force on the quality of PCD tools were systematical analyzed. The results showed that the fluid and grinding force seemed to have the same affecting pattern on the quality of PCD tools' flank face. When the main removal mechanism was micro cracking, the existence of the fluid and a larger grinding force would deteriorate the smoothness of PCD tools' flank face; while when the main removal mechanism was sliding wear, they seemed to both have little influence on the integrity of the flank face; but on the other side, both of them would enlarge the serration of PCD tools. Unlike the grinding fluid and grinding force, the grinding speed affected the grinding process in a different way. As the grinding speed increasing, the quality of the flank face and cutting edge of PCD tools improved firstly and deteriorated afterward. And the best grinding quality of PCD cutting tools could be achieved with a medium grinding speed.