Can SAE AMS 6418 be carburised?

[harsuda]

Can SAE AMS 6418 material be carburised? I am trying to carburise to increase the surface hardness to 55HRC.

 

[swall]

I am doubtful about sucessfully carburizing this material. First of all, the high silicon content (1.3-1.7) could be a problem. I have heard anecdotes about trying carburize (actually carbon restore) other high silicon alloys (namely Cr-Si spring material) and the carburization process just does not want to happen. Secondly, the high silicon content might tend to promote intergranular oxidation, even if a high carbon case could be developed. Finally, the high nickel content (1.6/2.0). Would tend to give you lots of retained austenite, especially if you had to bump up the carbon potential to compensate for the problems posed by the silicon.