Evaluate The Cutting Performance Of The Ceramic Cutting Tools Using Varied Depth-of-cut Turning And The Research On The Muremechanism Of The Ceramic Cutting Tools

Ceramic cutting tools (Si3N4> Al2O3) are particularly good for turning gray cast iron due to their high red hardness, wear resistance and chemical stability with gray cast iron. However, the intrinsic brittleness of Si3N4ceramics makes the cutting tools easy to be damaged when subjected to impact force. Hence, it need a suitable test method to measure the cutting performance of ceramic cutting tools. On the other hand, now,80%cutting tools have coatings. But most of the researches were focus on the function of increasing wear resistance and high-temperature behavior of the coatings. Due to the brittleness of ceramic materials, this paper not only study the wear resistance of coatings, but also research the function of toughening tools of the coatings. In the present work, turning experiments on gray cast iron were carried out by using four types Si3N4cutting tools and two types Al2O3cutting tools under continuous turning and varied depth-of-cut turning. Tool wear, tool life and chemical composition on worn flank faces and failure mechanism of the cutting tools were studied.The results show that:The tool life of the Si3N4cutting tools(SL550C and SC10) was increased about2-5times with the covering of TiN,Al2O3coating in continuous turning and varied depth-of-cut turning; The thickness and order of the coatings covered on the tools made a difference in the cutting performance of the Si3N4cutting tools; Si3N4cutting tools were more suitable for a severe cutting environment than Al2O3cutting tools; The dominant failure mechanism of the Si3N4cutting tools was abrasive wear in continuous turning and a combination of abrasive wear and chipping in varied depth-of-cut turning. In addition, adhesive wear also found to play a role in the tools failure to some extent for both uncoated and coated Si3N4cutting tools in continuous and varied depth-of cut turning; The dominant failure mechanism of the Al2O3cutting tools was abrasive wear in continuous turning and a combination of abrasive wear and fatigue wear in small varied depth-of-cut turning; The dominant failure mechanism of the Al2O3cutting tools was fatigue wear and flaking in large varied depth-of-cut turning; In addition, adhesive wear also found to play a role in the tools failure to some extent for both uncoated and coated Al2O3cutting tools in continuous and varied depth-of cut turning; The CVD TiN, Al2O3and PVD TiN coatings could not only improve the wear resistance of the cutting tools, but also increase the cutting toughness of the tools, In the other hand, the PVD TiN coatings could keep almost the same workpiece roughness with the substrate and the CVD TiN, Al2O3coatings keep a higher workpiece roughness than the substrate.