Plasma boronitriding has been successfully employed to overcome the difficulty in diamond growth on ferrous-based substrates. Commercial cobalt-sintered, tungsten-cemented carbides (WC(Co)) were pretreated by a plasm... Plasma boronitriding has been successfully employed to overcome the difficulty in diamond growth on ferrous-based substrates. Commercial cobalt-sintered, tungsten-cemented carbides (WC(Co)) were pretreated by a plasma boronitriding method, diamond was then deposited by microwave-enhanced chemical vapor deposition (MPCVD). The deposited films were characterized by scanning electron microscopy and Raman spectroscopy. Continuous diamond films with a sharp characteristic Raman peak of 1334 cm-1 were grown and adhered well on the boronitrided region of the cemented carbide substrates. On the other hand, a mixture of diamond crystallites, amorphous carbon and graphitic carbon was loosely deposited on the unboronitrided region. A cobalt inert thin layer formed after plasma boronitriding pretreatment enabled the subsequent nucleation and growth of a high-quality CVD diamond.展开更多
The frictional resistance and machining quality when cutting carbon fiber reinforced plastics (CFRP) laminates are associated with tribological behavior of tool materials. In the present study, the tribological proper...The frictional resistance and machining quality when cutting carbon fiber reinforced plastics (CFRP) laminates are associated with tribological behavior of tool materials. In the present study, the tribological properties of three types of monolayer microcrystalline diamond (MCD) coatings, nanocrystalline diamond (NCD) coatings and dual-layer MCD/NCD coatings sliding against CFRP are investigated under dry lubricated conditions using the rotational friction tester. The coefficients of friction (COF), wear rate and worn surfaces of the contacted surfaces are analyzed for the MCD-CFRP, NCD-CFRP and MCD/NCD-CFRP contacting pairs. The results show that compared with the monolayer MCD and NCD, the bilayer of MCD/NCD coating displays the lowest COF with the value of ~0.13, it is 42% and 55% of the values for MCD and NCD coatings. Due to the rough surfaces of MCD, the wear debris of CFRP on MCD samples exhibits the plowing effect. While for the NCD and MCD/NCD samples, the wear fragments display the planar shapes. The wear rate of CFRP against MCD is more than twice that of CFRP against NCD, due to the excellent loading capacity. While the wear rate of CFRP against MCD/NCD is about twice than that of CFRP-NCD pairs. The bilayer of MCD/NCD combines the excellent advantages of high hardness of MCD and the smooth surface of NCD. It shows the broad application potential for the bilayer coatings.展开更多
The WC 6%Co(mass fraction) substrate surfaces were chemically pretreated with the two step etching method, using Murakami reagent for 3～ 7?min, and then an φ (HNO 3)∶ φ (HCl)=4∶1 solution for 1～ 15?min. Diamond ...The WC 6%Co(mass fraction) substrate surfaces were chemically pretreated with the two step etching method, using Murakami reagent for 3～ 7?min, and then an φ (HNO 3)∶ φ (HCl)=4∶1 solution for 1～ 15?min. Diamond films were deposited on the substrates by a hot filament chemical vapor deposition reactor. The results show that the Co content of the substrate surfaces can be reduced from 6% to 0.12% within the etching depth of 5～ 10?μm, the surface roughness of the substrates is increased up to R a= 1.0?μm, as well as the substrates hardness is decreased from HRA 89.5 to HRA 84.2 after the two step etching. A slight preference towards {111} orientation can be observed from the XRD patterns and SEM micrograph of diamond film on WC 6%Co sample. The morphology of small rice like ballas diamond was observed on the WC 6%Co substrates. A typical Raman spectrum with a sharp peak at 1?332?cm -1 for the diamond film indicates that the deposited films are good quality polycrystalline diamond. The indentation testing shows that the adhesion between diamond film and the substrate after HF CVD deposition is good.展开更多
文摘 Plasma boronitriding has been successfully employed to overcome the difficulty in diamond growth on ferrous-based substrates. Commercial cobalt-sintered, tungsten-cemented carbides (WC(Co)) were pretreated by a plasma boronitriding method, diamond was then deposited by microwave-enhanced chemical vapor deposition (MPCVD). The deposited films were characterized by scanning electron microscopy and Raman spectroscopy. Continuous diamond films with a sharp characteristic Raman peak of 1334 cm-1 were grown and adhered well on the boronitrided region of the cemented carbide substrates. On the other hand, a mixture of diamond crystallites, amorphous carbon and graphitic carbon was loosely deposited on the unboronitrided region. A cobalt inert thin layer formed after plasma boronitriding pretreatment enabled the subsequent nucleation and growth of a high-quality CVD diamond.
文摘The frictional resistance and machining quality when cutting carbon fiber reinforced plastics (CFRP) laminates are associated with tribological behavior of tool materials. In the present study, the tribological properties of three types of monolayer microcrystalline diamond (MCD) coatings, nanocrystalline diamond (NCD) coatings and dual-layer MCD/NCD coatings sliding against CFRP are investigated under dry lubricated conditions using the rotational friction tester. The coefficients of friction (COF), wear rate and worn surfaces of the contacted surfaces are analyzed for the MCD-CFRP, NCD-CFRP and MCD/NCD-CFRP contacting pairs. The results show that compared with the monolayer MCD and NCD, the bilayer of MCD/NCD coating displays the lowest COF with the value of ~0.13, it is 42% and 55% of the values for MCD and NCD coatings. Due to the rough surfaces of MCD, the wear debris of CFRP on MCD samples exhibits the plowing effect. While for the NCD and MCD/NCD samples, the wear fragments display the planar shapes. The wear rate of CFRP against MCD is more than twice that of CFRP against NCD, due to the excellent loading capacity. While the wear rate of CFRP against MCD/NCD is about twice than that of CFRP-NCD pairs. The bilayer of MCD/NCD combines the excellent advantages of high hardness of MCD and the smooth surface of NCD. It shows the broad application potential for the bilayer coatings.
文摘The WC 6%Co(mass fraction) substrate surfaces were chemically pretreated with the two step etching method, using Murakami reagent for 3～ 7?min, and then an φ (HNO 3)∶ φ (HCl)=4∶1 solution for 1～ 15?min. Diamond films were deposited on the substrates by a hot filament chemical vapor deposition reactor. The results show that the Co content of the substrate surfaces can be reduced from 6% to 0.12% within the etching depth of 5～ 10?μm, the surface roughness of the substrates is increased up to R a= 1.0?μm, as well as the substrates hardness is decreased from HRA 89.5 to HRA 84.2 after the two step etching. A slight preference towards {111} orientation can be observed from the XRD patterns and SEM micrograph of diamond film on WC 6%Co sample. The morphology of small rice like ballas diamond was observed on the WC 6%Co substrates. A typical Raman spectrum with a sharp peak at 1?332?cm -1 for the diamond film indicates that the deposited films are good quality polycrystalline diamond. The indentation testing shows that the adhesion between diamond film and the substrate after HF CVD deposition is good.
