Abstract: An amorphous carbon film includes carbon as a major component, and silicon in an amount of from 0.1 atomic % or more to 10 atomic % or less when the entire amorphous carbon film is taken as 100 atomic %. The carbon is composed of carbon having an sp2 hybrid orbital in an amount of from 60 atomic % or more to 90 atomic % or less when the entire carbon amount is taken as 100 atomic %. Also disclosed is a process for producing the amorphous carbon film.

Abstract: An amorphous carbon film includes carbon as a major component, and silicon in an amount of from 0.1 atomic % or more to 10 atomic % or less when the entire amorphous carbon film is taken as 100 atomic %. The carbon is composed of carbon having an sp2 hybrid orbital in an amount of from 60 atomic % or more to 90 atomic % or less when the entire carbon amount is taken as 100 atomic %. Also disclosed is a process for producing the amorphous carbon film.

Abstract: A method for producing cast iron gears includes the steps of heating a blank composed of cast iron and having a teeth forming part to such a temperature that at least the teeth forming part is at least austenitized, and hot rolling the teeth forming part of the blank by pressing projecting teeth of a rolling machine against the teeth forming part which is in a hot state and within an austenitized range, while cooling the blank, thereby generating a teeth part in the teeth forming part of the blank. Hot rolling with a low plastic deformation resistance prevents lowering of strength due to the exposure of graphite particles of cast iron and occurrence of quenching cracks and rolling cracks, and improves gear accuracy.