Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using...Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.展开更多
Electro-spark deposition（ESD） was adopted for preparing high property coatings by depositing WC-8Co cemented carbide on an spheroidal graphite roll substrate.The microstructure and properties of the coating were inv...Electro-spark deposition（ESD） was adopted for preparing high property coatings by depositing WC-8Co cemented carbide on an spheroidal graphite roll substrate.The microstructure and properties of the coating were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） with energy dispersive X-ray（EDX） and ball-disc configuration wear tester.The results show that nanosized particles and amorphous structures prevail in the coating which is metallurgically bonded to the substrate.The microstructures of the transition zone include columnar structure and equiaxed structure.The primary phases of the coating contain W2C, W6C2.54, Fe3W3C, and Co3W3C.The results of abrasive test show that the coating has low friction coefficients（μaverage = 0.18） and the wear mechanisms are mainly abrasive wear, fatigue wear, and oxidation wear.The maximum microhardness value of the coating is about 17410 N/mm2.The study reveals that the electro-spark deposition process has better coating quality and the coating has high wear resistance and hardness.展开更多
To prepare high wear resistance and high hardness coatings, electro-spark deposition was adopted for depositing an electrode of a mixture of 92wt%WC＋8wt%Co on a cast steel roll substrate. The coating was characterize...To prepare high wear resistance and high hardness coatings, electro-spark deposition was adopted for depositing an electrode of a mixture of 92wt%WC＋8wt%Co on a cast steel roll substrate. The coating was characterized by classical X-ray diffractometer （XRD） and scanning electron microscopy （SEM） with energy dispersive X-ray analysis （EDX）. The results indicate that the coating shows nanosized particulate structure and dendritic structure including columnar structure and equiaxed structure. The primary phases of the coating contain Fe3W3C, Co3W3C, Fe2C and Si2W. The coating has a low friction coefficient of 0.13, its average wear-resistance is 3.3 times that of the cast steel roll substrate and the main mechanism is abrasive wear. The maximum microhardness value of the coating is about 1573.9 Hv0.3. The study reveals that the electro-spark deposition process has the characteristic of better coating quality and the coating has higher wear resistance and hardness.展开更多
The cobalt-based alloy coating with different Co contents was deposited on 45 steel by electro-spark deposition with the self-made electrode. The coating has a compact and uniform microstructure with low porosity and ...The cobalt-based alloy coating with different Co contents was deposited on 45 steel by electro-spark deposition with the self-made electrode. The coating has a compact and uniform microstructure with low porosity and no visible microcracks. When Co content increases grad- ually, oxygen content of coating samples 1-5 decreases first and then increases in the range of 2.52 wt%-3.05 wt%; sample 3 has the lowest oxygen content of 2.52 %. Mi- crohardness of the coating is improved remarkably com- pared with the substrate （HV 230.18）. With Co content increasing, microhardness of the coating samples 1-5 first rises slightly and then declines rapidly in the range of HV 580.61-1052.33. Sample 3 gets the maximum of HV 1052.33, which is about 4.6 times that of the substrate. The coating presents excellent wear resistance, which first increases and then decreases when Co content increases. Sample 3 shows the best wear resistance of about 6.4 times that of the substrate. Main wear mechanism of the coating is abrasive wear and fatigue wear, along with oxidation wear under high speed or heavy load conditions.展开更多
WC-(W,Cr)2C-Ni coating was prepared on 1Cr18Ni9Ti stainless steel and C-276 Ni-base Hastelloy by high velocity oxy-fuel(HVOF)spraying.The effect of post heat treatment in air atmosphere on the microstructure,phase com...WC-(W,Cr)2C-Ni coating was prepared on 1Cr18Ni9Ti stainless steel and C-276 Ni-base Hastelloy by high velocity oxy-fuel(HVOF)spraying.The effect of post heat treatment in air atmosphere on the microstructure,phase composition,microhardness,fracture toughness,and wear resistance of HVOF-sprayed WC-(W,Cr)2C-Ni coating was investigated.The microstructure and phase composition of the coatings were analyzed by means of field emission scanning electron microscopy(FESEM)and X-ray diffraction(XRD).The microhardness and fracture toughness of the coatings were measured using a microhardness tester and a Vickers hardness tester.Moreover,dry friction and wear behavior of the coatings sliding against Si3N4 ball was investigated using an oscillating friction and wear tester;and the worn surfaces of the coatings were analyzed by means of scanning electron microscopy(SEM).It was found that heat treatment within 500-800°C resulted in crystallization of amorphous phase in as-sprayed coating,generating nanoscale new phases such as NiWO4,CrWO4 and Cr2WO6.Besides,heat treatment led to increase of the microhardness of as-sprayed coating,and the highest microhardness was obtained after heat treatment at 800°C.The fracture toughness and wear resistance of the as-sprayed coating increased with increasing heat treatment temperature up to 700°C but tended to decrease with further elevating temperature.In other words,the mechanical properties and wear resistance of the as-sprayed coatings were worsened owing to excessive growth of oxidation grains and depletion of ductile Ni binder after heat treatment above 700°C.Thus it was suggested that as-sprayed ceramic composite coating should be post heat treated in air at a moderate temperature of 700°C so as to achieve the optimized mechanical properties and wear resistance.展开更多
基金supported by Key Projects of Strategic International Scientific and Technological Innovation Cooperation(Grant No.2016YFE0201300)
文摘Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.
基金supported by the International Science and Technology Cooperation Project of the Ministry of Science and Technology of China (No. 2006DFA52240)
文摘Electro-spark deposition（ESD） was adopted for preparing high property coatings by depositing WC-8Co cemented carbide on an spheroidal graphite roll substrate.The microstructure and properties of the coating were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） with energy dispersive X-ray（EDX） and ball-disc configuration wear tester.The results show that nanosized particles and amorphous structures prevail in the coating which is metallurgically bonded to the substrate.The microstructures of the transition zone include columnar structure and equiaxed structure.The primary phases of the coating contain W2C, W6C2.54, Fe3W3C, and Co3W3C.The results of abrasive test show that the coating has low friction coefficients（μaverage = 0.18） and the wear mechanisms are mainly abrasive wear, fatigue wear, and oxidation wear.The maximum microhardness value of the coating is about 17410 N/mm2.The study reveals that the electro-spark deposition process has better coating quality and the coating has high wear resistance and hardness.
基金supported by the International Science and Technology Cooperation Project of the Ministry of Science and Technology of China (No.2006DFA52240)
文摘To prepare high wear resistance and high hardness coatings, electro-spark deposition was adopted for depositing an electrode of a mixture of 92wt%WC＋8wt%Co on a cast steel roll substrate. The coating was characterized by classical X-ray diffractometer （XRD） and scanning electron microscopy （SEM） with energy dispersive X-ray analysis （EDX）. The results indicate that the coating shows nanosized particulate structure and dendritic structure including columnar structure and equiaxed structure. The primary phases of the coating contain Fe3W3C, Co3W3C, Fe2C and Si2W. The coating has a low friction coefficient of 0.13, its average wear-resistance is 3.3 times that of the cast steel roll substrate and the main mechanism is abrasive wear. The maximum microhardness value of the coating is about 1573.9 Hv0.3. The study reveals that the electro-spark deposition process has the characteristic of better coating quality and the coating has higher wear resistance and hardness.
基金financially supported by the National Natural Science Foundation of China (No. 50875261)
文摘The cobalt-based alloy coating with different Co contents was deposited on 45 steel by electro-spark deposition with the self-made electrode. The coating has a compact and uniform microstructure with low porosity and no visible microcracks. When Co content increases grad- ually, oxygen content of coating samples 1-5 decreases first and then increases in the range of 2.52 wt%-3.05 wt%; sample 3 has the lowest oxygen content of 2.52 %. Mi- crohardness of the coating is improved remarkably com- pared with the substrate （HV 230.18）. With Co content increasing, microhardness of the coating samples 1-5 first rises slightly and then declines rapidly in the range of HV 580.61-1052.33. Sample 3 gets the maximum of HV 1052.33, which is about 4.6 times that of the substrate. The coating presents excellent wear resistance, which first increases and then decreases when Co content increases. Sample 3 shows the best wear resistance of about 6.4 times that of the substrate. Main wear mechanism of the coating is abrasive wear and fatigue wear, along with oxidation wear under high speed or heavy load conditions.
基金Innovative Group Foundation from National Natural Science Foundations of China(50421502)National"973"Project(2007CB607601)
文摘WC-(W,Cr)2C-Ni coating was prepared on 1Cr18Ni9Ti stainless steel and C-276 Ni-base Hastelloy by high velocity oxy-fuel(HVOF)spraying.The effect of post heat treatment in air atmosphere on the microstructure,phase composition,microhardness,fracture toughness,and wear resistance of HVOF-sprayed WC-(W,Cr)2C-Ni coating was investigated.The microstructure and phase composition of the coatings were analyzed by means of field emission scanning electron microscopy(FESEM)and X-ray diffraction(XRD).The microhardness and fracture toughness of the coatings were measured using a microhardness tester and a Vickers hardness tester.Moreover,dry friction and wear behavior of the coatings sliding against Si3N4 ball was investigated using an oscillating friction and wear tester;and the worn surfaces of the coatings were analyzed by means of scanning electron microscopy(SEM).It was found that heat treatment within 500-800°C resulted in crystallization of amorphous phase in as-sprayed coating,generating nanoscale new phases such as NiWO4,CrWO4 and Cr2WO6.Besides,heat treatment led to increase of the microhardness of as-sprayed coating,and the highest microhardness was obtained after heat treatment at 800°C.The fracture toughness and wear resistance of the as-sprayed coating increased with increasing heat treatment temperature up to 700°C but tended to decrease with further elevating temperature.In other words,the mechanical properties and wear resistance of the as-sprayed coatings were worsened owing to excessive growth of oxidation grains and depletion of ductile Ni binder after heat treatment above 700°C.Thus it was suggested that as-sprayed ceramic composite coating should be post heat treated in air at a moderate temperature of 700°C so as to achieve the optimized mechanical properties and wear resistance.
