| 摘要 |
PURPOSE:To obtain a piston having partially improved resistance to thermal impact and thermal fatigue by forming an alloyed cast iron layer in which Ni is incorporated at a specific ratio and block graphite is crystallized and dispersed to the prescribed section in the piston head part of the cast iron piston down to an adequate depth. CONSTITUTION:Ni or Ni-Fe alloy is disposed onto the surface in the section such as hot spot part 4 at the peripheral edge of a recessed ejection port 3, etc. in the piston head part 2 of the cast iron piston 1 and high-density energy such as laser is irradiated thereon from above. The Ni, etc., disposed on the surface and the base material surface layer made on cast iron thereunder are thereby quickly melted and quickly solidifed. The alloyed cast iron layer which contains 10-60wt% Ni and has the matrix consisting of austenite or essentially consisting of austenite and in which the block graphite is uniformly dispersed and crystallized is thereby formed into the above-mentioned hot spot part 4 down to >=0.2mm depth from the surface and the cast iron piston having the improved resistance to thermal impact and thermal fatigue in said section for an internal combustion engine is obtd. |
