This paper presents a comparison of two-component ammonia-based inlet atmospheres diluted with either hydrogen (NH₃/H₂) or nitrogen (NH₃/N₂). Taking advantage of the features of inlet atmospheres diluted with nitrogen and hydrogen, four two-stage processes were designed and carried out, which were juxtaposed with two single-stage processes carried out only in an NH₃ atmosphere. A common parameter of the processes carried out was the same value of nitrogen availability in each process stage. The gas nitriding process was carried out on ASIS 1085 non-alloy steel and ASIS 52100 alloy steel. It was found that the chemical composition of the steels studied, for the adopted nitriding process parameters, did not affect the kinetics of the growth in the mass of nitrided samples as a function of the nitriding time. However, the additions of alloying elements present in the steels studied significantly affected the nitrogen distribution between the resulting iron nitride layer and the diffusion zone in the nitrided substrate. Because of the presence of chromium in AISI 52100 steel, a larger mass of nitrogen accumulated in the nitriding zone in the solution compared with unalloyed AISI 1085 steel. As a result, with the same increase in the mass of nitrided steel, a thicker layer of iron nitrides formed on AISI 1085 steel than on AISI 52100 steel.

This paper proposes a mathematical description of nitriding atmospheres obtained from a one-component ammonia ingoing atmosphere and a two-component ammonia inlet nitrogen-diluted atmosphere. The Fe-N phase equilibrium diagrams of the nitriding atmosphere in the hydrogen content-temperature (Q-T) system for selected NH₃/N₂ atmosphere compositions are presented. The nitriding atmosphere obtained with different degrees of nitrogen dilution of the ingoing atmosphere was characterized. It has been shown that in processes carried out in nitriding atmospheres obtained from a two-component atmosphere with nitrogen, there is no direct relationship between the value of the nitrogen potential and the degree of dilution of the ingoing atmosphere with nitrogen. It has been shown analytically and confirmed experimentally that with changes in the degree of dilution of ammonia with nitrogen, the hydrogen content of the nitriding atmosphere and, consequently, the nitrogen availability of the nitriding atmosphere change. Using the example of nitriding AISI 52100 steel, it has been experimentally demonstrated that the change in nitrogen availability, caused by a change in the degree of dilution of the ingoing atmosphere with nitrogen, is not accompanied by a change in the value of the nitrogen potential. It has also been shown that the change in the nitrogen availability of the nitriding atmosphere, induced by the change in the composition of the aNH₃/bN₂ ingoing atmosphere, affects the kinetics of nitrogen mass gain in the nitrided layer and the distribution of nitrogen mass between the iron nitride layer and the solution zone. It has also been shown that with the change in nitrogen availability, what changes in addition to the thickness of the iron nitride layer is also the phase composition of the layer. Using gravimetric tests, the mass of nitrogen in the iron nitride layer and the solution zone has been determined. To describe the equilibrium between the NH₃/H₂ atmosphere and nitrogen in the different iron phases, a modified Lehrer diagram in the coordinate system of temperature and hydrogen content in the nitriding atmospheres (T-Q) has been proposed.

The aim of the research discussed in the manuscript was to check the availability of control of nitrogen decomposition processes on nitrided AISI 52100 and AISI 1010 steels during annealing at 520 °C in N₂ and at 600 °C in H₂. The tests have shown that when annealing AISI 1010 steel at a temperature of 520 °C in N₂ under a pressure of 200 Pa for 2 h, an ε → γ’ + N₂↑ phase transformation occurs. Over the next 3 h, the ε phase disappears and the γ’ phase gradually transforms into Feα(N). When annealing AISI 52100 steel, the denitrification process is faster; after 2 h there is a complete transformation of ε → γ’ + N₂↑, and in the next 3 h, there is a complete transformation of γ’-Feα(N). During annealing in H₂ at a temperature of 600 °C, the denitrification processes are most intense; the complete transformation of γ’ → Feα(N) + N₂ occurs after 45 min of the process. When annealing nitrided AISI 1010 steel in nitrogen at atmospheric pressure, phase transformation (ε → γ’ + N₂↑) and weight loss of the sample are observed only in the first 20 min of the process, then the sample weight increases. This was the result of the formation of iron oxide, which also inhibited the denitrification process of the iron nitride layer.

Insect antennae are covered in hairlike sensilla that detect diverse environmental cues. Selection on these functions has produced a bewildering variety of antennal forms, including many examples of sexual dimorphism (SD). Antenna length SD is particularly common, but poorly understood, in longhorned beetles (Coleoptera: Cerambycidae). Extremely elongate male antennae may extend the reach of individuals searching for mates, enabling rapid recognition via antennal contact. Alternatively, they may increase sensitivity to airborne pheromones by bearing more olfactory sensilla. We tested these hypotheses by modeling sensillum distributions and abundances across species and sexes of Anoplistes, a cerambycid genus with extensive variation in antenna length and SD. We found limited evidence that olfactory sensillum abundance scales with antenna segment length; instead, mechano‐ and contact chemosensory sensilla cluster near the antenna tip, consistent with contact‐mediated mate recognition. If the tip segment serves an important tactile role, that may explain why it is exceptionally elongated in males of several species with long, sexually dimorphic antennae. In other Anoplistes species with strong antennal SD, however, all segments exhibit similar levels of dimorphism. Collectively, our results suggest that alternative pathways to antenna SD evolved rapidly in Anoplistes, perhaps due to different patterns of selection on tactile sensation.