The -pH diagram of Ni-W-P-H2O system at 298.15 K,10 1325 Pa was plotted by thermodynamic calculation software FactSageTM 5.1. The results show that tungsten and phosphorus can be co-deposited with nickel in type of ...The -pH diagram of Ni-W-P-H2O system at 298.15 K,10 1325 Pa was plotted by thermodynamic calculation software FactSageTM 5.1. The results show that tungsten and phosphorus can be co-deposited with nickel in type of Ni4W,Ni3P,Ni5P2,respectively. XRD analysis shows that the main phase of RE-Ni-W-P-B4C coatings is amorphous as deposited. After heated at 673 K for 3 h,part phases change to crystalline which are Ni,Ni3P,P,W,Ni3C,Ni3B,CeO2. SEM shows the micrograph of the coatings is even and the solid particles scatter well. The thickness of the coating is 2 219 μm after electroplating for 96 h. The micro-hardness of the coatings is HV 825-HV 1 097 as-deposited and increases to HV 1 236 after heat treated. The wear resistance of the coatings is good and the friction coefficient changes from 0.10 to 0.33 during the abrasion process. The resistance to oxidation of the composite coatings is better than Ni-W-P alloy coatings and worse than that of RE-Ni-W-P-SiC coatings.展开更多
The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,struc...The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,structure and micro-hardness. The morphology and structure of the Ni-P-SiC composite coatings were studied by scanning electron microscopy(SEM) and X-ray diffractometry(XRD),respectively. A great deal of particles incorporation and uniform distribution were found in Ni-P-SiC composite coatings. XRD results show a broad peak of nickel and low intensity SiC peaks present on as-deposited condition. Micro-hardness of as-deposited Ni-P-SiC composite coatings is improved greatly,and the best micro-hardness is obtained after heat treatment in a high vacuum at 400 ℃ .展开更多
Taking a bath with basic nickel carbonate as the source of nickel,sodium hypophosphite as the reducing agent and citric acid as the complexing agent,the Ni-P coatings on AZ91D magnesium alloy were prepared. The influe...Taking a bath with basic nickel carbonate as the source of nickel,sodium hypophosphite as the reducing agent and citric acid as the complexing agent,the Ni-P coatings on AZ91D magnesium alloy were prepared. The influence of pH value of the bath on the content of phosphorus,microhardness and corrosion resistance of the deposits was examined. The XRD analysis results show that the Ni-P coatings plated under all conditions have a mixed microstructure of amorphous and nanocrystalline and undergo a phase transformation to crystalline nickel and nickel phosphide upon heat-treatment. The microhardness of the Ni-P coatings increases with the increase of pH value of the bath and has a maximum at pH=6. The potentiodynamic polarization test in 3.5%(mass fraction) NaCl solution reveals that the Ni-P coatings exhibit a very good corrosion resistance to protecting AZ91D magnesium alloy.展开更多
基金Project (2005XZ1) supported by the Scientific Research Key Foundation of Wuhan University of Science and Technology, China
文摘The -pH diagram of Ni-W-P-H2O system at 298.15 K,10 1325 Pa was plotted by thermodynamic calculation software FactSageTM 5.1. The results show that tungsten and phosphorus can be co-deposited with nickel in type of Ni4W,Ni3P,Ni5P2,respectively. XRD analysis shows that the main phase of RE-Ni-W-P-B4C coatings is amorphous as deposited. After heated at 673 K for 3 h,part phases change to crystalline which are Ni,Ni3P,P,W,Ni3C,Ni3B,CeO2. SEM shows the micrograph of the coatings is even and the solid particles scatter well. The thickness of the coating is 2 219 μm after electroplating for 96 h. The micro-hardness of the coatings is HV 825-HV 1 097 as-deposited and increases to HV 1 236 after heat treated. The wear resistance of the coatings is good and the friction coefficient changes from 0.10 to 0.33 during the abrasion process. The resistance to oxidation of the composite coatings is better than Ni-W-P alloy coatings and worse than that of RE-Ni-W-P-SiC coatings.
基金Projects(05B008) supported by Scientific Research Fund of Hunan Provincial Education Departmentproject(104014) supported by Fok Ying Tong Education Foundation of Ministry of Education
文摘The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,structure and micro-hardness. The morphology and structure of the Ni-P-SiC composite coatings were studied by scanning electron microscopy(SEM) and X-ray diffractometry(XRD),respectively. A great deal of particles incorporation and uniform distribution were found in Ni-P-SiC composite coatings. XRD results show a broad peak of nickel and low intensity SiC peaks present on as-deposited condition. Micro-hardness of as-deposited Ni-P-SiC composite coatings is improved greatly,and the best micro-hardness is obtained after heat treatment in a high vacuum at 400 ℃ .
基金Project(2004CB619301) supported by the National Key Basic Research Development Program of ChinaProject supported by 985 Project of Jilin University
文摘Taking a bath with basic nickel carbonate as the source of nickel,sodium hypophosphite as the reducing agent and citric acid as the complexing agent,the Ni-P coatings on AZ91D magnesium alloy were prepared. The influence of pH value of the bath on the content of phosphorus,microhardness and corrosion resistance of the deposits was examined. The XRD analysis results show that the Ni-P coatings plated under all conditions have a mixed microstructure of amorphous and nanocrystalline and undergo a phase transformation to crystalline nickel and nickel phosphide upon heat-treatment. The microhardness of the Ni-P coatings increases with the increase of pH value of the bath and has a maximum at pH=6. The potentiodynamic polarization test in 3.5%(mass fraction) NaCl solution reveals that the Ni-P coatings exhibit a very good corrosion resistance to protecting AZ91D magnesium alloy.
