Effect of NaCl and CaCl2 additives on NaNO3 bath nitriding of steel

A study has been made of nitriding of interstitial-free steel sheet specimens in the sodium nitrate bath. The nitriding rate increased when the bath contained a small amount of sodium chloride and calcium chloride. Accordingly, the tensile strengths and hardness values of the steel specimens nitrided in the chloride containing bath were higher than those of the same steel specimens nitrided in the pure nitrate bath when the nitriding time and temperature were controlled so that the excessive formation of brittle compound Fe4N could be prevented.