The Influence of Selected Process Parameters on the Efficiency of the Process of Gas Nitriding of AISI 1085 Steel

The main aim of the manuscript was to investigate the impact of modifying the parameters of the gas nitriding process of samples made from AISI 1085 steel on the course and results of the process carried out in a chemical reactor allowing for thermogravimetric measurements. The tested steel was subjected in a chemical reactor to the process of gas nitriding in the temperature range of 490-580 °C, using different sample heating rates (in the range of 1-25 °C/min) and various mixtures of nitriding gases (pure NH₃, or NH₃ with the addition of H₂ or N₂). To assess the impact of the tested process parameters on its efficiency, the thickness of the nitrided layers produced, the change in sample mass, the structure of the phases produced, the phase composition and the microhardness were examined. For the research methodology used, it was found that reducing the amount of NH₃ and/or using H₂ or N₂ admixtures adversely affects the thickness of the nitride layers produced. At the same time, the use of a lower maximum process temperature with the same gas mixture resulted in a significant difference in the thickness of the layers. It was also found that the use of pure NH₃ or a gas mixture (NH₃ + H₂) with higher NH₃ contents resulted in higher surface microhardnesses of the samples and that for these samples, the hardness increased to a greater depth.