Study On The Preparation And Cutting Performance Of Micro-nano Composite Gradient Self-lubricating Ceramic Tool

In order to crack down the problem that self-lubricating ceramic tools are notreasonable balance between antifriction and wear resistance performance, a new type ofmicro-nano composite gradient self-lubricating ceramic tool materials was developed bythe method of micro-nano composite and gradient composite design. TiB2/WC/h-BNmicro-nano composite gradient self-lubricating ceramic tool materials with nano-TiB2and micro-TiB2as matrix, WC as the reinforcing phase, h-BN as solid lubricant weresuccessfully developed by hot-pressing technology. The cutting tool materialscomponent, gradient distribution, microstructure, mechanical properties and cuttingperformance were studied.TiB2/WC/h-BN micro-nano composite gradient self-lubricating ceramic toolmaterials were prepared by dispersing and blending powders with wet process,laminated padding and hot pressure technology. The mechanical properties ofTiB2/WC/h-BN micro-nano composite gradient self-lubricating ceramic tool materialshave been greatly improved. Compared with the homogeneous TiB2/WC/h-BNself-lubricating ceramic tool material, the grains of micro-nano composite gradientself-lubricating ceramic tool materials with addition of nanometer TiB2were refined,and its flexural strength, fracture toughness and hardness were increased by15.8%,6.7%and11.1%, repectively.A systematic study of layers and components distribution index n on micro-nanocomposite gradient self-lubricating ceramic tool materials has been made.When thecomponent distribution index n is1.1, with the increase of layers, hardness and flexuralstrength of micro-nano composite gradient self-lubricating ceramic tool materials weredecreased, and the fracture toughness was increased first and then decreased. When thelayer is five, with the increase of component distribution index n, the mechanicalproperties of micro-nano composite gradient self-lubricating ceramic tool material wereincreased first and then decreased. The optimal flexural strength, fracture toughness andhardness were791MPa,4.91MPa·m1/2and16GPa, repectively.The cross section and the microstructure of bending fractured surfaces of micro-This work was supported by the National Natural Science Foundation of China (51075248), theProgram for New Century Excellent Talents in University (NCET-10-0866) and ShandongProvincial Natural Science Foundation for Distinguished Young Scholars (JQ201014) nano composite gradient self-lubricating ceramic tool materials were observed andanalyzed. Its toughening mechanism was studied and mainly includes the transgranularfracture and intergranular fracture mixed mode, crack deflection, crack bridging andcrack branching.The residual stress of micro-nano composite gradient self-lubricating ceramic toolmaterial was tested. The stress distribution trends of indentation crack method and thefinite element method are the same, which is symmetrical distribution on the middlelayer and increased first and then decreased. There is residual stress in tool material,especially residual compressive stress exists on the surface of tool material by thegradient design. When cutting experiment, the cutting force can be partially offset byresidual compressive stress.The wear mechanism of micro-nano composite gradient self-lubricating ceramictool was studied and analyzed when continuous cutting of45steel and cast iron. Theinfluence of cutting speed on tool flank wear and tool life was analyzed. The tool flankwear was increased with the increase of cutting speed. With the increase of cuttingspeed, tool life of TN1and TN2cutting tools were increased first and then decreased.The wear mechanism of TN1and TN2are abrasive wear and adhesive wear. Theevolution of the self-lubricating film was analyzed, and self-lubricating film includesthe generation process, damage, loss and regeneration. So the micro-nano compositegradient self-lubricating ceramic tool in its life cycle always has been self-lubricatingfunction. Wear resistance and friction performance of TN2tool are better than TN1tool.Gradient design of micro-nano composite gradient self-lubricating ceramic tool materialcan effectively improve the cutting performance.