Formation of the nitride case on low-carbon stainless steels

Abstract

1. Nitrides differing in dispersity were observed in electron microscopic studies of the case on lowcarbon stainless steels 000Kh 18 and 000Kh18N9. The surface zone consists mainly of coalesced nitrides 700 A in size. At the boundary with the base metal most of the nitrides are finely dispersed (70–90 A). The increase in hardness at the interface is explained by the high dispersity of the chromium nitrides. 2. Lowering the carbon content and increasing the purity of steels Kh18 and Kh 18N9 lead to an increase of the case depth by 30–40% with some reduction of the hardness and increase of the corrosion resistance. 3. Stainless steels of high purity are simpler to process (can be nitrided without a depassivator) and show no tendency to form a nitride network, which is one of the reasons for brittleness of the case.