Cubic boron nitride(cBN)superabrasive grinding wheels exhibit unique advantages in the grinding of difficult-to-cut materials with high strength and toughness,such as titanium alloys and superalloys.However,grinding w...Cubic boron nitride(cBN)superabrasive grinding wheels exhibit unique advantages in the grinding of difficult-to-cut materials with high strength and toughness,such as titanium alloys and superalloys.However,grinding with multilayered metallic cBN superabrasive wheels faces problems in terms of grain wear resistance,the chip storage capability of the working layers and the stability and controllability of the dressing process.Therefore,in this work,novel metallic cBN superabrasive wheels with aggregated cBN(AcBN)grains and open pore structures were fabricated to improve machining efficiency and surface quality.Prior to the grinding trials,the airborne abrasive blasting process was conducted and the abrasive blasting parameters were optimized in view of wear properties of cBN grains and metallic matrix materials.Subsequently,the comparative experiments were performed and then the variations in grinding force and force ratio,grinding temperature,tool wear morphology and ground surface quality of the multilayered AcBN grinding wheels were investigated during machining Ti-6Al-4V alloys.In consideration of the variations of grain erosion wear volume and material removal rate per unit of pure metallic matrix materials as the abrasive blasting parameters changes,the optimal abrasive blasting parameters were identified as the SiC abrasive mesh size of 60#and the abrasive blasting distance and time of 60 mm and 15 s,respectively.The as-developed AcBN grains exhibited better fracture toughness and impact resistance than monocrystalline cBN(McBN)grains because of the existence of metal-bonded materials amongst multiple cBN particles that decreased crack propagation inside whole grains.The metallic porous AcBN wheels had lower grinding forces and temperature and better ground surface quality than vitrified McBN wheels due to the constant layer-by-layer exposure of cBN particles in the working layer of AcBN wheels.展开更多
Grinding with cubic boron nitride(CBN)superabrasive is a widely used method of machining superalloy in aerospace industries.However,there are some issues,such as poor grinding quality and severe tool wear,in grinding ...Grinding with cubic boron nitride(CBN)superabrasive is a widely used method of machining superalloy in aerospace industries.However,there are some issues,such as poor grinding quality and severe tool wear,in grinding of powder metallurgy superalloy FGH96.In addition,abrasive wheel wear is the significant factor that hinders the further application of CBN abrasive wheels.In this case,the experiment of grinding FGH96 with single CBN abrasive grain using different parameters was carried out.The wear characteristics of CBN abrasive grain were analyzed by experiment and simulation.The material removal behavior affected by CBN abrasive wear was also studied by discussing the pile-up ratio during grinding process.It shows that morphological characteristics of CBN abrasive grain and grinding infeed direction affect the CBN abrasive wear seriously by simulation analysis.Attrition wear,micro break,and macro fracture had an important impact on material removal characteristics.Besides,compared with the single cutting edge,higher pile-up ratio was obtained by multiple cutting edges,which reduced the removal efficiency of the material.Therefore,weakening multiple cutting edge grinding on abrasive grains in the industrial production,such as applying suitable dressing strategy,is an available method to improve the grinding quality and efficiency.展开更多
Diamond/Cu-Sn-Ti composites have been successfully prepared by cold-press forming in conjunction with high-temperature vacuum active brazing at 1223 K.Ensuing wetting behaviors between diamond and filler metal,interfa...Diamond/Cu-Sn-Ti composites have been successfully prepared by cold-press forming in conjunction with high-temperature vacuum active brazing at 1223 K.Ensuing wetting behaviors between diamond and filler metal,interfacial characteristics of the reaction layer,and wear resistance of the bulky composite have been fully investigated.It is revealed that all diamond particles can only be fully coated when the TiH_(2)content exceeds 5 wt%,below which sharp edges on diamond can still be observed.The interfacial reaction layer is found to be composed of TiC,the thickness of which is demonstrated to increase as a function of TiH_(2)content,arriving at the peak value of 1.70μm and remaining almost constant afterwards.It is further shown that the maximum wear resistance occurs approaching 5 wt%TiH_(2)content.Potential mechanisms responsible for such interesting phenomena have been postulated.展开更多
1.Introduction Fracture toughness is the ability of materials against both the initiation and propagation of cracks[1],which is a crucial mechanical property for safety-critical applications of structural materials.Al...1.Introduction Fracture toughness is the ability of materials against both the initiation and propagation of cracks[1],which is a crucial mechanical property for safety-critical applications of structural materials.Although the yield strength of ceramics is significantly higher than that of metallic materials,the fracture toughness is severely lower than that of metallic materials due to the strongly directional covalent bonding[1-3].For a long time,how to improve the fracture toughness of ceramics without the deterioration of strength(or hardness)has been one of the most challenging problems in materials science.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51921003,92160301 and 52175415)the Fundamental Research Funds for the Central University(No.NP2022441)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Open Foundation State Key Laboratory of Mechanical Transmissions(No.SKLMT-MSKFKT-202101).
文摘Cubic boron nitride(cBN)superabrasive grinding wheels exhibit unique advantages in the grinding of difficult-to-cut materials with high strength and toughness,such as titanium alloys and superalloys.However,grinding with multilayered metallic cBN superabrasive wheels faces problems in terms of grain wear resistance,the chip storage capability of the working layers and the stability and controllability of the dressing process.Therefore,in this work,novel metallic cBN superabrasive wheels with aggregated cBN(AcBN)grains and open pore structures were fabricated to improve machining efficiency and surface quality.Prior to the grinding trials,the airborne abrasive blasting process was conducted and the abrasive blasting parameters were optimized in view of wear properties of cBN grains and metallic matrix materials.Subsequently,the comparative experiments were performed and then the variations in grinding force and force ratio,grinding temperature,tool wear morphology and ground surface quality of the multilayered AcBN grinding wheels were investigated during machining Ti-6Al-4V alloys.In consideration of the variations of grain erosion wear volume and material removal rate per unit of pure metallic matrix materials as the abrasive blasting parameters changes,the optimal abrasive blasting parameters were identified as the SiC abrasive mesh size of 60#and the abrasive blasting distance and time of 60 mm and 15 s,respectively.The as-developed AcBN grains exhibited better fracture toughness and impact resistance than monocrystalline cBN(McBN)grains because of the existence of metal-bonded materials amongst multiple cBN particles that decreased crack propagation inside whole grains.The metallic porous AcBN wheels had lower grinding forces and temperature and better ground surface quality than vitrified McBN wheels due to the constant layer-by-layer exposure of cBN particles in the working layer of AcBN wheels.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.92160301,52175415)Major Special Projects of Aero-engine and Gas Turbine(Grant No.2017-VII-0002-0095)Funding for Outstanding Doctoral Dissertation in NUAA(Grant No.BCXJ19-06).
文摘Grinding with cubic boron nitride(CBN)superabrasive is a widely used method of machining superalloy in aerospace industries.However,there are some issues,such as poor grinding quality and severe tool wear,in grinding of powder metallurgy superalloy FGH96.In addition,abrasive wheel wear is the significant factor that hinders the further application of CBN abrasive wheels.In this case,the experiment of grinding FGH96 with single CBN abrasive grain using different parameters was carried out.The wear characteristics of CBN abrasive grain were analyzed by experiment and simulation.The material removal behavior affected by CBN abrasive wear was also studied by discussing the pile-up ratio during grinding process.It shows that morphological characteristics of CBN abrasive grain and grinding infeed direction affect the CBN abrasive wear seriously by simulation analysis.Attrition wear,micro break,and macro fracture had an important impact on material removal characteristics.Besides,compared with the single cutting edge,higher pile-up ratio was obtained by multiple cutting edges,which reduced the removal efficiency of the material.Therefore,weakening multiple cutting edge grinding on abrasive grains in the industrial production,such as applying suitable dressing strategy,is an available method to improve the grinding quality and efficiency.
基金the support from the National Natural Science Foundation of China(Nos.52104360 and U20A20277)Research Fund for Central Universities(Nos.N2025025 and N2125024)+5 种基金Project funded by China Postdoctoral Science Foundation(Nos.2020TQ0060 and 2020M680965)Postdoctoral research fund of Northeastern University(No.20210202)the State Key Laboratory of Tribology,Tsinghua University(No.SKLTKF20B14)State Key Laboratory of Solid Lubrication,Lanzhou Institute of Chemical Physics,Chinese Academy of Sciences(No.LSL-2003)State Key Laboratory of Advanced Brazing Filler Metals and Technology,Zhengzhou Research Institute of Mechanical Engineering Co.,LTD(No.SKLABFMT202002)supported by the Fund of the State Key Laboratory of Solidification Processing,Northwestern Polytechnic University(Grant No.SKLSP202114)。
文摘Diamond/Cu-Sn-Ti composites have been successfully prepared by cold-press forming in conjunction with high-temperature vacuum active brazing at 1223 K.Ensuing wetting behaviors between diamond and filler metal,interfacial characteristics of the reaction layer,and wear resistance of the bulky composite have been fully investigated.It is revealed that all diamond particles can only be fully coated when the TiH_(2)content exceeds 5 wt%,below which sharp edges on diamond can still be observed.The interfacial reaction layer is found to be composed of TiC,the thickness of which is demonstrated to increase as a function of TiH_(2)content,arriving at the peak value of 1.70μm and remaining almost constant afterwards.It is further shown that the maximum wear resistance occurs approaching 5 wt%TiH_(2)content.Potential mechanisms responsible for such interesting phenomena have been postulated.
基金financially supported by the Natural Science Foundation of Hebei Province of China(Nos.E2016203425 and E2017203223)the Key Projects of Scientific and Technological Research in Hebei Province(No.ZD2017074)+1 种基金the National Natural Science Foundation of China(No.12075215)the Science and Technology Project of Hebei Education Department(No.QN2021136 and ZD2017026)。
文摘1.Introduction Fracture toughness is the ability of materials against both the initiation and propagation of cracks[1],which is a crucial mechanical property for safety-critical applications of structural materials.Although the yield strength of ceramics is significantly higher than that of metallic materials,the fracture toughness is severely lower than that of metallic materials due to the strongly directional covalent bonding[1-3].For a long time,how to improve the fracture toughness of ceramics without the deterioration of strength(or hardness)has been one of the most challenging problems in materials science.