In the present work,mechanical alloying of a powder mixture of nickel and graphite(up to 15wt%)was carried out in an attrition mill under a nitrogen atmosphere.The as-milled powders were characterized by scanning elec...In the present work,mechanical alloying of a powder mixture of nickel and graphite(up to 15wt%)was carried out in an attrition mill under a nitrogen atmosphere.The as-milled powders were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),and transmission electron microscopy(TEM).The 15wt%graphite dissolved into the nickel(exceeding the negligible solid solubility in the nickel–carbon system),thereby forming a supersaturated solid solution of graphite in a nickel matrix.The dissolved graphite occupied interstitial positions along the dislocation edges and at the grain-boundary regions.A three-step graphite dissolution mechanism has been proposed.The associated changes in the nickel lattice,such as changes in the crystallite size(62 to 43 nm),lattice strain(0.12%to 0.3%),and lattice parameter(0.3533 to 0.3586 nm),which led to the formation of the supersaturated solid solution,were also evaluated and discussed.展开更多
This study explores the fabrication of Fe-based amorphous/crystalline coating by air plasma spraying and its dependency on the coating parameters(plasma power,primary gas flow rate,powder feed rate,and stand-off dista...This study explores the fabrication of Fe-based amorphous/crystalline coating by air plasma spraying and its dependency on the coating parameters(plasma power,primary gas flow rate,powder feed rate,and stand-off distance).X-ray diffraction of the coatings deposited at optimized spray parameters showed the presence of amorphous/crystalline phase.Coatings deposited at a lower plasma power and highest gas flow rate exhibited better density,hardness,and wear resistance.All coatings demonstrated equally good resistance against the corrosive environment(3.5wt%NaCl solution).Mechanical,wear,and tribological studies indicated that a single process parameter optimization cannot provide good coating performance;instead,all process parameters have a unique role in defining better properties for the coating by con-trolling the in-flight particle temperature and velocity profile,followed by the cooling pattern of molten droplet before impingement on the substrate.展开更多
文摘In the present work,mechanical alloying of a powder mixture of nickel and graphite(up to 15wt%)was carried out in an attrition mill under a nitrogen atmosphere.The as-milled powders were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),and transmission electron microscopy(TEM).The 15wt%graphite dissolved into the nickel(exceeding the negligible solid solubility in the nickel–carbon system),thereby forming a supersaturated solid solution of graphite in a nickel matrix.The dissolved graphite occupied interstitial positions along the dislocation edges and at the grain-boundary regions.A three-step graphite dissolution mechanism has been proposed.The associated changes in the nickel lattice,such as changes in the crystallite size(62 to 43 nm),lattice strain(0.12%to 0.3%),and lattice parameter(0.3533 to 0.3586 nm),which led to the formation of the supersaturated solid solution,were also evaluated and discussed.
文摘This study explores the fabrication of Fe-based amorphous/crystalline coating by air plasma spraying and its dependency on the coating parameters(plasma power,primary gas flow rate,powder feed rate,and stand-off distance).X-ray diffraction of the coatings deposited at optimized spray parameters showed the presence of amorphous/crystalline phase.Coatings deposited at a lower plasma power and highest gas flow rate exhibited better density,hardness,and wear resistance.All coatings demonstrated equally good resistance against the corrosive environment(3.5wt%NaCl solution).Mechanical,wear,and tribological studies indicated that a single process parameter optimization cannot provide good coating performance;instead,all process parameters have a unique role in defining better properties for the coating by con-trolling the in-flight particle temperature and velocity profile,followed by the cooling pattern of molten droplet before impingement on the substrate.
