| The excellent physical and chemical properties of synthetic diamond make it widely used in manufacturing and semiconductor fields.Ni-Cr alloy is a typical cemented carbide,and diamond is one of the ideal materials for efficient machining.However,the solid-state chemical reaction of Ni-Cr alloy during processing leads to excessive wear,which seriously affects the service life and processing quality of diamond.Moreover,Ni-Cr alloy as a common diamond tool binder,the study of the solid-state reaction mechanism provides an important theoretical basis for the comprehensive development of diamond tools.Therefore,this subject has clarified the solid-state reaction mechanism between Ni-Cr alloy and diamond(100)and(111)crystal planes through temperature control experiments below the liquidus of Ni-Cr alloy.Based on first-principles calculations,the interfacial element diffusion behavior at the initial stage of the reaction between Ni-Cr alloy and diamond(100)and(111)crystal planes is explained.Finally,through the solid-state mechanism,the dynamic chemical wear products of diamond machining Ni-Cr alloy are discussed,which provides theoretical support for the efficient machining of Ni-Cr alloy.In addition,the effect of Ni-Cr alloy on the diamond interface morphology in the solid state provides a new research idea and direction for the interface regulation of large-scale wafer diamond materials.Specifically,the research work included in this paper can be summarized as follows:1.Carry out the heat treatment experiment of diamond particles that have been coated with Ni-Cr alloy and its elemental metal below the liquidus temperature in a vacuum furnace,and study the different crystal planes of diamond particles and Ni-Cr alloy solid-state reaction mechanism.Among them,the change of diamond surface morphology under the influence of Ni-Cr alloy at different temperatures provides theoretical support for the realization of diamond interface control.2.The supercell model of Ni-Cr alloy and diamond different crystal planes is established by first-principles simulation calculation.The phase transformation behavior of diamond two crystal planes is clear at the initial stage of the reaction.In contrast to the variation,the migration and diffusion behaviors of Nickel and Chromium atoms supplement the demonstration of the solid-state reaction mechanism between Ni-Cr alloy and diamond with different crystal planes.3.Under the solid-state interaction mechanism and the first-principles simulation experiments,the processing and wear experiments of diamond(100)and(111)crystal planes on metal Ni,Cr and Ni-Cr alloy were carried out,and the main chemical wear products and removal rate of the diamond surface were clarified.It provides a certain theoretical support for the research of efficient machining of Ni-Cr alloy.Through the research and analysis of this work,the main conclusions obtained in this paper are summarized as follows:1.Temperature control experiments show that Ni and Ni-Cr alloys can induce partial graphitization phase transformation on the diamond surface at 400 °C,while diamond has a comprehensive and rapid phase transformation at 700 ℃,and the degree of graphitization and crystallinity are greatly improved.Meanwhile,the carbonization reaction between Ni-Cr alloy and diamond happened at 700 ℃.2.The carbonization reaction rate of diamond(111)crystal plane is faster than that of(100)crystal plane under the action of Ni-Cr alloy at 700 °C.3.In the simulation results,the Ni-Cr alloy shows an obvious carbonization reaction trend on the(111)crystal plane of diamond,and the alloy structure is stable in the(100)crystal plane,but it catalyzes the reconstruction of the diamond surface structure,showing a clear graphitization trend.4.Simulation and dynamic wear research present that the diamond(100)crystal face wears the fastest,and the main phase transformation products are graphite phase when machining Ni and Ni-Cr alloys,and amorphous carbon phase when machining Cr,among which Ni-Cr alloys wear fastest. |
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