Variation of High Temperature Gas Nitriding Time on Duplex Stainless Steels

This report presents the discussion on solution nitriding of duplex stainless steel. It consists of project's background, literature review, methodology, and all the relevant process and component related to this project. Nitriding is a surface-hardening heat treatment which introduces nitrogen into the surface of the duplex stainless steels at certain temperature range. The objectives of this project are to investigate the hardness and the changes on the surface microstructure of nitrided duplex stainless steel. During nitriding sample will exposed to a constant high temperature at 11 00°C with varying the time which is at lh, 2.5 h, 4.5h and 6 h. Metallographic study, XRD examination and assessment of the sample's hardness will be performed to examine the hardness of the treated sample. Scanning Electron Micrograph (SEM) and optical microscope will be used to do an assessment of the microstructure of the sample before nitriding and after nitriding process to be conducted. Weight of the nitrided sample at constant temperature 11 00°C are increasing as the nitriding time increase. The microstructure observed for the nitrided sample shows that the grain course of austenite phases are increasing as longer time nitriding were conducted as compared to ferrite phases. It shows that austenite phases react more in nitrogen diffusion compared to ferrite. Highest value of hardness: 448.2HV is achieved from sample nitrided at 1100 oc for 6 hours. Diffusion of nitrogen content leads to higher hardness. XRD analysis also shows that the appearance of FeN increase the hardness of the material. Hence as a conclusion, the objectives of the project are achieved successfully. High Temperature Gas Nitriding at ll00°C has successfully improved the hardness of the material due to more nitrogen diffused in it

The study of metal nitride layer formation by solid-state reactions

A new solid-state reaction to form metal nitrides has been investigated. It was confirmed that single phase chromium nitride is formed by a solid-state diffusion reaction between iron nitride and chromium chloride powders at temperatures between 570-700°C. The discovered reaction can be applied to form chromium nitride coatings on tool steels for metal forming applications

Variation of High Temperature Gas Nitriding Time on Duplex Stainless Steels

This report presents the discussion on solution nitriding of duplex stainless steel. It consists of project's background, literature review, methodology, and all the relevant process and component related to this project. Nitriding is a surface-hardening heat treatment which introduces nitrogen into the surface of the duplex stainless steels at certain temperature range. The objectives of this project are to investigate the hardness and the changes on the surface microstructure of nitrided duplex stainless steel. During nitriding sample will exposed to a constant high temperature at 11 00°C with varying the time which is at lh, 2.5 h, 4.5h and 6 h. Metallographic study, XRD examination and assessment of the sample's hardness will be performed to examine the hardness of the treated sample. Scanning Electron Micrograph (SEM) and optical microscope will be used to do an assessment of the microstructure of the sample before nitriding and after nitriding process to be conducted. Weight of the nitrided sample at constant temperature 11 00°C are increasing as the nitriding time increase. The microstructure observed for the nitrided sample shows that the grain course of austenite phases are increasing as longer time nitriding were conducted as compared to ferrite phases. It shows that austenite phases react more in nitrogen diffusion compared to ferrite. Highest value of hardness: 448.2HV is achieved from sample nitrided at 1100 oc for 6 hours. Diffusion of nitrogen content leads to higher hardness. XRD analysis also shows that the appearance of FeN increase the hardness of the material. Hence as a conclusion, the objectives of the project are achieved successfully. High Temperature Gas Nitriding at ll00°C has successfully improved the hardness of the material due to more nitrogen diffused in it

The Expanded Phases Formed in Stainless Steels by Means of Low-Temperature Thermochemical Treatments: A Corrosion Perspective

Surface engineering of stainless steels using thermochemical treatments at low temperatures has been the subject of intensive research for enhancing the surface hardness of these alloys without impairing their corrosion resistance. By using treatment media rich in nitrogen and/or carbon, it is possible to inhibit chromium compound formation and obtain supersaturated solid solutions, known as expanded phases, such as expanded austenite or S-phase in austenitic stainless steels, expanded ferrite in ferritic grades, and expanded martensite in martensitic grades. These low-temperature treatments produce a significant increase in surface hardness, which improves wear and fatigue resistance. However, the corrosion behavior of the modified surface layers remains of paramount importance. In the international literature, many studies on this topic are reported, but the results are not always univocal, and there are still open questions. In this review, the corrosion behavior of the expanded phases and the modified layers in which they are present is critically analyzed and discussed. The relationships between the phase composition and the microstructure of the modified layers and the corrosion resistance are highlighted while also considering the different test conditions. Furthermore, corrosion test methods are discussed, and suggestions are given for improving the measurements. Finally, perspectives on future directions for investigation are suggested for encouraging further research

The Analysis and Control of Distortion in Carbonitrided and Nitrocarburized Plain Carbon Steels

The main objective of this study was to compare the carbonitriding and gaseous ferritic nitrocarburizing processes. The driving force behind this research was to be able to use these results to determine the potential of ferritic nitrocarburizing as a suitable replacement to the carbonitriding process currently being used to impart a hard, wear resistant case on the surface of SAE 1010 steel torque converter pistons. The carbonitriding and ferritic nitrocarburizing processes were evaluated with respect to physical, mechanical, and metallurgical properties. The processes were compared quantitatively using distortion, retained austenite, and residual stress values, and qualitatively through optical and scanning electron microscopy. All test specimens were machined from low carbon steel and heat treated according to specified schedules. While the carbonitrided conditions were similar to those of the current production schedule, conditions for the nitrocarburized test specimens incorporated a range of processing times and temperatures. The results from this study support the use of gaseous ferritic nitrocarburizing as a means of reducing size and shape distortion in the torque converter pistons. Not only were distortion values lower after heat treatment, but the lack of retained austenite within the steel decreases the likelihood of further distortion associated with the delayed transformation of austenite to martensite. Although these findings do support the use of the nitrocarburizing process, the presence of tensile stresses measured at the surface of the pistons warrant the need for additional wear testing. Until such tests are performed, a change in process to gaseous ferritic nitrocarburizing cannot be endorsed