Even if the furnace components in these processes are constructed of more resistant materials, the cyclic exposure to the carburizing/nitriding environment will eventually lead to an excessive pick-up of carbon and/or nitrogen.  This will lead to problems such as embrittlement due to precipitation of carbides/nitrides and impaired corrosion resistance as a result of the simultaneous chromium depletion.

These effects can also occur for other reasons, e.g. carburization due to oil residues on heat treated components and nitridation due to overheating in nitrogen containing gases or to cracking ammonia.

The resistance of high temperature alloys to carbon and nitrogen pick-up increases primarily with increasing nickel content but also with increasing contents of silicon and chromium.  353 MA is therefore the better of the MA grades, but 253 MA has also performed well under certain conditions in carburizing environments, despite of its lower alloy content.

Experience has shown that it takes only minor amounts of oxygen in the furnace gas (e.g. even in the form of carbon dioxide or steam) to produce a thin and tough oxide layer on 253 MA, which provides good protection against pick-up of both carbon and nitrogen.