Category: Nitriding and Nitrocarburizing

Improving the Nitriding Process Using ZeroFlow® Gas Nitriding Technology

Gas nitriding has been performed for almost a century with many variations over the years. The benefits of nitriding are well documented and nitriding has gained amazing industrial acceptance. However, the equipment and control of the nitrided layer has continued to be challenging, and as such, nitriding is still slowly being adopted by industry, but the rate of change is improving.

One Minute Mentor: Effects of Nitrocarburizing on Stainless Steel

Electrochemical measurements show that transpassivity (which is necessary for the onset of pitting) of expanded austenite occurs at appreciably higher applied voltages than for austenite with the same metallic composition but without nitrogen.

One Minute Mentor: Hardness Depth Profiles of Stainless Steel after Nitriding and Nitrocarburizing

X-ray diffraction analysis indicates that the hardened case consists of a mixture of expanded austenite and expanded martensite.

One Minute Mentor: Nitrocarburizing in a Carrier Gas

Nitrocarburizing in a carrier gas to which (initially solid) urea was added led to a fast growth of the expanded austenite zone. The gaseous decomposition products of urea that develop in the furnace are highly activating, which means that activation and nitrocarburizing are achieved simultaneously.

One Minute Mentor: Residual Stress Profiles as Determined by X-Ray Diffraction

For nitrocarburizing or consecutive carburizing and nitriding, the typical stress profile is smoother than for nitriding only.

One Minute Mentor: Residual Stress Profiles

Residual stress profiles of nitrided austenitic AISI 316 are shown in the graph.

One Minute Mentor: Nitrogen-Expanded Austenite

The graph shows hardness-depth profiles of nitrided AISI 316. A profile for carburizing is shown for comparison.

One Minute Mentor: Control of Nitriding Potential at Low Temperatures

The graph shows the case thickness for fluidized-bed nitrided 316L samples after 8 hours of treatment.

One Minute Mentor: Nitriding in Fluidized-Bed Reactors at Low Temperatures

In nitriding treatment furnaces, the heating is done electrically, and the fluidizing gas composition is chosen to provide the optimum chemistry for the desired surface treatment (usually a mixture of NH3 + N2, with CH4 added when nitrocarburizing is desired).

One Minute Mentor: High-Temperature Nitriding for Deeper Case

High-temperature nitriding or solution nitriding at temperatures of 2010 ± 90°F is a new treatment available to produce cases with nitrogen concentrations in the range of 0.4 to 0.9 wt%, which is low compared to plasma nitriding treatments at low temperature (up to 16.9wt% N), but the resulting case is up to 100 times deeper (2 mm, or 0.08 in.).