{"id":12361,"date":"2025-11-11T12:45:54","date_gmt":"2025-11-11T12:45:54","guid":{"rendered":"https:\/\/www.jstconsultancy.cz\/?p=10237"},"modified":"2026-07-31T22:19:24","modified_gmt":"2026-07-31T22:19:24","slug":"how-to-correctly-distinguish-lpc-iv-lpcn","status":"publish","type":"post","link":"https:\/\/intelligent-kalam.80-240-27-133.plesk.page\/en\/how-to-correctly-distinguish-lpc-iv-lpcn\/","title":{"rendered":"How to correctly distinguish LPC IV \u2013 LPCN"},"content":{"rendered":"

I already wrote about carbonitriding \u00a0under reduced pressure last year. https:\/\/intelligent-kalam.80-240-27-133.plesk.page\/nitrocementace-jak-na-to-v-lpc\/<\/a>. My conclusion that the LPCN process <\/strong>is feasible is valid, but I have been instructed that it is a little different.<\/p>\n

I had the honor to meet Ben Kahle, who developed this technology for ALD and later for ECM. His position is as follows:<\/p>\n

“During the eight years that I have been deeply involved in low-pressure carbonitriding (LPCN), new surprises and challenges have constantly emerged. Unlike conventional atmospheric carburizing, LPCN is a <\/strong>process that is still not fully developed or universally mastered by anyone in the world” <\/em><\/p>\n

So much for the quote. It was a bit shocking, but such a P\u0159enosil has been dealing with this process all his life. Unlike conventional carbonitriding, \u00a0the fundamental problem with LPCN<\/strong> is that acetylene and ammonia cannot be admitted at the same time, due to the formation\u00a0 of HCN<\/strong> according to the scheme below.<\/p>\n

C (graphite) + NH\u2083 + C\u2082H\u2082 \u2192 HCN <\/strong>+ other products (e.g. H\u2082, N\u2082)<\/p>\n

 <\/p>\n

Ben describes the experiment:<\/p>\n

“steel 16MnCr5, process at 870 C, 90 min, graphite chamber, total active area 1 m2<\/sup>, only NH3<\/sub> is allowed. Despite this fact, the resulting layer contains 0.6\u20130.7% nitrogen and about 0.75% carbon. But where did the carbon come from, when we only allowed NH3<\/sub>? The answer is the formation of HCN<\/strong> in the contact of ammonia with graphite elements of the heating chamber”<\/em><\/p>\n

In short, HCN<\/strong> is a critical and unavoidable part of the process in LPCN<\/strong>, but probably also in classical carbonitriding, if we had a graphite heater and graphite lining. The fact that we don’t have it is unlucky. Because if that were the case, P\u0159enosil would already know about this problem.<\/p>\n

But why is this such a problem? As we have explained in the previous chapters, if the reaction of C2<\/sub>H2<\/sub> \u2192 2 C + H2<\/sub> takes place, then all the carbon from the catalytic reaction is consumed as part of diffusion into the steel. But this is not the case with ammonia. There, the reaction C (graphite) + NH3<\/sub> \u2192 HCN<\/strong> + H2<\/sub> is again a catalytic reaction, but not only from contact with the batch surface, but also from contact with graphite heating elements, furnace wall, CFC fixtures or from soot deposits in the hot zone. And because this area is basically still the same, the amount of HCN <\/strong>will be the same, even if the batch surface area will be different. This will significantly complicate the control of the carbonitriding process with different parts surfaces. If we fine-tune the carbonitriding \u00a0process to a reference batch of 1 m2, the result will be completely different for another batch with other parts and an surface area of 20 m2. And that’s what Ben claims.<\/p>\n

In that last post, I was a supporter of admitting ammonia in the first step. I don’t think so anymore. The reason is not only the different nitrogen and carbon content from catalytic reactions, but the problem is also in the reverse diffusion of nitrogen. Because as soon as I turn off the ammonia, I have a two-sided gradient, i.e. both towards the steel and into the atmosphere, and the nitrogen will slowly disappear from the layer with the formation of N2. Again, I quote Ben:<\/p>\n