What happens to the hydrogen gas?

I will answer quickly for David because he is out of the country. I think your answer can be found with the previous blog from David. He indicates that it goes to exhaust.

If that answer isn't good enough, please follow-up, and we will have David reply when he returns to the states. Thanks for your interest!

A supplier has indicated that their gas nitriding process will be switched from the Floe (two-stage) method to a single-stage nitride process. If all product inspections remain the same, will this represent a significant process change?

A supplier has indicated that their gas nitriding process will be switched from the Floe (two-stage) method to a single-stage nitride process. If all product inspections remain the same, will this represent a significant process change?

I also am curious about the single-stage vs. double-stage question. However, my specific question is about the effect of longer soak times during the second stage, holding all other factors constant. What does this typically do to the part?

Any experience out there?

Question 1 the hydrogen gas that is produced by the decomposition of ammonia, reconstitutes itself with the nitrogen gas on cooling. In other words it reverts back to ammonia minus the amount of nitrogen that has been used for diffusion into the steel.
Question 2. The purpose of the Floe process is to reduce the thickness of the surface compound layer by reducing the nitrogen availability to the work surface. This will simply reduce the thickness of a compound layer. The diffusion layer below the compound layer will remain as formed stable nitrides. The case depth will be slightly deeper using the floe process over the same period of time simply because it is processed at a higher process temperature. The single stage notch writing process uses a lower process temperature than that of the floe process. The compound layer resulting from the single stage process will be thicker. However the steel chemistry/analysis will influence the thickness of the compound layer.
Question 3. With a reference once again to the double stage/floe process, if the total cycle time that is used for single stage as would be used for double stage nitride, then the case that will be deeper simply because a higher process temperature has been selected for the double stage nitride process. The temperature increase from single stage to do with stage will be approximately 75°F to 100°F. The difference will be of course in the formed case that the compound layer will be thinner. The risk with the higher process temperature that is used for the double stage procedure is that the gaseous dissociation must be very carefully controlled as it can result in the formation of nitride networks, for example on sharp corners. The nitride networks can be seen microscopically as fingerlike white streaks flowing from the compound layer and into the diffusion zone of the stable nitrides.

I am confused. In the double process the dissociation is elevated. Based on the following passage of the text:
"Consequently, the nitrogen activity is a function of the number of ammonia molecules dissociated at the steel surface per unit of time."
shouldn't the higher dissociation level cause a thicker white layer instead of reducing it?