鋳鉄に処理した無電解Ni-Pメッキの特性

抄録

  The effect of graphite shape, surface roughness and heat treatment on strength of Ni-P alloy films on cast iron has been studied. The Ni-P alloy films plated were deposited on gray cast iron, nodular cast iron and compared with carbon steel by electroless plating. The plated specimens were evaluated by bending test, hardness measurement and X-ray diffraction. The results obtained here are as fallows ;
  (1) Cracks induced by the bending test initiate near the interface between the plating film and the base metal and propagate into the film in the case of cast irons. In the carbon steel, the origins were observed at the surface of the plating film.
  (2) Strength of plating films were not found to be influenced by the surface roughness under R max 200μm and the thickness of the plating film less than 40μm.
  (3) Heat treatment changed the crystal structure of the plating film. Ni₃P, NiP₂ and Ni₂P were identified as precipitation products in the plating film heated at temperatures higher than 300°C although only (111) plane of Nikel was found in the X-ray diffraction patters of the films heated at temperatures lower than 300°C.
  (4) The precipitation of Ni₃P, NiP₂ and Ni₂P decrease the fracture toughness measured by the identation method and the bending strength of the plating film. However, decreasing the precipitation amount of NiP₂ may improve the toughness of the film.