Low Temperature Ferritic Nitrocarburizing

Salt bath nitrocarburizing (SBN™) is typically done at 1075°F, thereby limiting near-surface hardening, and consequently fatigue strengthening, according to the temper resistance of the base material. The first phase of this investigation is a study of the response of low alloy steels to SBN at lower temperatures, viz. 750°F-950°F (400°C-510°C). Based on metallographic and traverse hardness results, it is evident that SAE 4140 and SAE 8620 (carb.) steels can develop satisfactory near-surface hardening by low temperature SBN, particularly at 950°F (510°C) with extended time cycles. The next phase of the investigation is to determine the correlation of increased near-surface hardness on bending and contact fatigue strengths.