In this work, the Zr C-SiC composite coatings were co-deposited by chemical vapor deposition(CVD)using ZrCl4, MTS, CH4 and H2 as raw materials. The morphologies, compositions and phases of the composite coatings were ...In this work, the Zr C-SiC composite coatings were co-deposited by chemical vapor deposition(CVD)using ZrCl4, MTS, CH4 and H2 as raw materials. The morphologies, compositions and phases of the composite coatings were characterized by scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDS) and X-ray diffraction(XRD). The results indicated that the morphologies, compositions and phases of the composite coatings were related to the deposition temperature, the flow rate of the carrier H2 gas, and the ratio of C/Zr. Moreover, the co-deposition mechanism of the composite coatings was also studied. It was found that different deposition temperatures resulted in different deposition mechanisms. At temperatures in the range of 1150–1250℃, the Zr C-SiC co-deposition was controlled by the surface kinetic process. At temperatures in the range of 1250–1400℃, the Zr C-SiC co-deposition was controlled by the mass transport process.展开更多
Four kinds of ZrC coatings with nearly the same thickness have been successfully prepared on graphite substrate by chemical vapor deposition(CVD) through controlling the ratio of inlet reacting gases.From backscat-ter...Four kinds of ZrC coatings with nearly the same thickness have been successfully prepared on graphite substrate by chemical vapor deposition(CVD) through controlling the ratio of inlet reacting gases.From backscat-tered electron images,it can be inferred that ZrCⅢcoating has the best tightness of all coatings.Meanwhile,line energy spectrum curve shows that zirconium and carbon elements distribute uniformly along the normal direction of the ZrCⅢcoating.As for varied microstructures,the coatings show different mechanical properties and residue stress.The strength and elastic modulus of ZrCⅢcoating were up to 89.57 and 1192.5 GPa,respectively.Those make it near the level of diamond.Value of residue tensile stress of ZrC+C composite coating was only 7.729 MPa and that of ZrCⅢcoatings was 349.632 MPa.The strong combination of small-size grains in ZrCⅢcoating plays a decisive role to the best mechanical properties.However,strong misfit of lattice between ZrCⅢcoating and substrate can induce high residue stress.展开更多
The effects of gradient structure on the microstructure and properties of coated cemented carbides were researched with optical microscopy （OM）, scanning electron microscopy （SEM）, strength measurements, and cutti...The effects of gradient structure on the microstructure and properties of coated cemented carbides were researched with optical microscopy （OM）, scanning electron microscopy （SEM）, strength measurements, and cutting tests. It shows that vacuum sintering of WC-Ti（C, N）-TaC-Co cemented carbides results in the formation of a surface ductile zone. The ductile zone prevents crack propagation and leads to the increase of transverse rupture strength of the substrate. The impact resistance of coated gradient inserts was obviously improved on the basis of maintaining resistance to abrasion and the forming mechanism of the gradient structure was also analyzed.展开更多
文摘In this work, the Zr C-SiC composite coatings were co-deposited by chemical vapor deposition(CVD)using ZrCl4, MTS, CH4 and H2 as raw materials. The morphologies, compositions and phases of the composite coatings were characterized by scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDS) and X-ray diffraction(XRD). The results indicated that the morphologies, compositions and phases of the composite coatings were related to the deposition temperature, the flow rate of the carrier H2 gas, and the ratio of C/Zr. Moreover, the co-deposition mechanism of the composite coatings was also studied. It was found that different deposition temperatures resulted in different deposition mechanisms. At temperatures in the range of 1150–1250℃, the Zr C-SiC co-deposition was controlled by the surface kinetic process. At temperatures in the range of 1250–1400℃, the Zr C-SiC co-deposition was controlled by the mass transport process.
基金the National Basic Research Program of (973) China(No.2011CB605805)the Postdoctor Fund of Central South University(No.20101210)
文摘Four kinds of ZrC coatings with nearly the same thickness have been successfully prepared on graphite substrate by chemical vapor deposition(CVD) through controlling the ratio of inlet reacting gases.From backscat-tered electron images,it can be inferred that ZrCⅢcoating has the best tightness of all coatings.Meanwhile,line energy spectrum curve shows that zirconium and carbon elements distribute uniformly along the normal direction of the ZrCⅢcoating.As for varied microstructures,the coatings show different mechanical properties and residue stress.The strength and elastic modulus of ZrCⅢcoating were up to 89.57 and 1192.5 GPa,respectively.Those make it near the level of diamond.Value of residue tensile stress of ZrC+C composite coating was only 7.729 MPa and that of ZrCⅢcoatings was 349.632 MPa.The strong combination of small-size grains in ZrCⅢcoating plays a decisive role to the best mechanical properties.However,strong misfit of lattice between ZrCⅢcoating and substrate can induce high residue stress.
文摘The effects of gradient structure on the microstructure and properties of coated cemented carbides were researched with optical microscopy （OM）, scanning electron microscopy （SEM）, strength measurements, and cutting tests. It shows that vacuum sintering of WC-Ti（C, N）-TaC-Co cemented carbides results in the formation of a surface ductile zone. The ductile zone prevents crack propagation and leads to the increase of transverse rupture strength of the substrate. The impact resistance of coated gradient inserts was obviously improved on the basis of maintaining resistance to abrasion and the forming mechanism of the gradient structure was also analyzed.
