XM19 is an alternative designation for the more highly alloyed austenitic stainless steel most commonly known as Nitronic® 50. It is used in ASTM A182, ASTM A276 and ASTM A479, alongside the unified numbering system caption UNS S20910.
Nitronic 50 is a higher-performance austenitic stainless steel that provides roughly twice the yield strength of regular 3xx-series stainless steels, with improved corrosion performance. Like some super duplex stainless steels, it uses increased nitrogen content to raise strength, so is sometimes called a nitrogen-strengthened alloy. Manganese additions add further strength through solid-solution strengthening.
It is widely used across marine and industrial applications. Compared with Alloy 316L it has increased chromium and molybdenum, which support its improved corrosion resistance: where Alloy 316L has a pitting resistance equivalent number (PREN) of 25, Nitronic 50 has a PREN of 34. It is listed in NACE MR0175 for sour-service applications thanks to its resistance to sulphide stress cracking.