Influence of annealing conditions on ion nitriding of martensitic stainless steel

Lattice expansion in austenitic stainless steel after nitrogen insertion in the temperature range between 320 and 380 °C is a well established phenomena whereas conflicting data on the existence of expanded phases in martensitic stainless steels are published. However, inferring the structure from X-ray diffraction data alone can be misleading, as the distinction between a martensite structure with a very low nitrogen content obtained after rapid quenching and a ferrite/cementite mixture after additional annealing is not straightforward. s presentation the results of nitrogen plasma immersion ion implantation (PIII) into differently preheated steels (martensite and ferrite structure of 1.4034 (X46Cr13), 1.4057 (X17CrNi16.2), 1.4021 (X20Cr13) and 1.4104 (X14CrMoS17)) are reported. X-ray diffraction (XRD) data and N to Fe ratios obtained from time-of-flight secondary ion mass spectroscopy (SIMS) are presented together with hardness values. The influence of the treatment parameters was investigated. A wear reduction of a factor of 10–100 was found for all implanted samples, whereas initially brittle martensites showing largest decrease.