Determination of interstitial nitrogen content in austenitic stainless steel welds by thermoelectric power
Angelique N. Lasseigne
Nitrogen is utilized as an interstitial solid solution strengthener in austenitic stainless steels. With increasing use of high nitrogen steels it is necessary to precisely quantify the nitrogen content to attain beneficial mechanical properties and corrosion resistance. High nitrogen contents partition into interstitial nitrogen and transition metal nitrides in austenitic stainless steel alloy 1.4565 welds, thus affecting the resulting material properties. Through the application of solid state physics concepts, a non-destructive surface contact probe utilizing thermoelectric power has been developed to conveniently assess and quantitatively map soluble nitrogen content in nitrogen strengthened austenitic stainless steel weldments. The thermoelectric power coefficient has been measured on plasma arc welds on nitrogen-strengthened austenitic stainless steel Alloy 1.4565, which has been interstitially strengthened with nitrogen for enhancement in mechanical properties and corrosion resistance.