HOMEFAQsBOOKS JOBS: Help WantedSuggestions you are here: Hotline/Forum => Letter 12141
Ion vs. Gas nitriding of H13 Tool Steel
I currently work for a warm forging company. Currently, all of our H13 dies used for warm(1600-2000 degrees)of carbon steel are ion nitrided. We experience good tool life, but when our furnace is down, we have tried gas nitriding and find the dies wear even faster than if we had not used a surface treatment at all. What differences between the two processes would cause this extreme difference in tool life? Should we avoid using gas nitriding on H13 tool steel?
Laura Brink- Canton, Ohio
Hello Laura!
What kind of white layer are you getting with the ion nitriding, and how does it differ from that given by the gas nitriding? That's the first question I'd focus on, as I suspect the compound zone created by the ion process is giving you the wear resistance you want.
Good luck!
|
Lee Gearhart |
Hi Laura,
There are a few reasons for the poor life of gas nitrided H13 dies.
1. Gas nitriding is much slower than ion (or plasma) nitriding and hence requires longer time of treatment for getting the same nitrided case depth. If the die had been gas nitrided for the same duration as in ion nitriding, the case depth would be lower and hence the wear resistance would also be lower.
2. In gas nitriding, ammonia gets dissociated catalytically on the surface of the workpiece to release nascent nitrogen which gets into the surface. There exists a possibility that dissociation may not be effective at some isolated pockets within the retort due to poor circulation and in these regions nitriding would not effective.
3. Another possibilty is that the white layer may not have been suppressed during nitriding or may not have been removed, if it had formed, after nitriding. In such a case, the layer would crumble and cause wear.
4. Yet another reason for the superior performance of ion nirided case is that the case is a monophase layer of either epsilon nitride or gamma prime depending on the application. Such tailoring of the case microstructure is not possible in gas nitridin.
Dr N KrishnarajFree lance Consultant - Chennai, India
What was the final outcome? Did you solve the mystery of gas nitriding.We are using an Electrospark Deposited coating which works well.
Dr. Ram K. Iyengar- Huntington, WV
We electo-spark deposited a superalloy on H-13 mandrels used for extrusion of superalloy tubes. Without the surface treatment we get from 8 to 30 extrusions per mandrel. With the superalloy coating we get from 30 to 100 extrusions per mandrel. The variation is due to the different alloys extruded, the size of the billet, the reduction ratio, the wall diameter etc.
Does the ion nitriding give better result than say 100 extrusions per mandrel?
Dr. Ram K. Iyengar- Huntington, WV
There is a very distinctive difference between the gas nitride and the ion nitride. The difference is in the resultinvg metallurgy from gas nitriding. With gas nitriding, the process is reliant on the decomposition of ammonia. The decomposition relies on the surface o0f the steel acting as a catalyst during the reactionasry period of the process cycle. As a result of the decomposition ,and becasue of fixed gas the surface metallurgy is fixed. This means the surface will consist of the compound layer which is a mixture of two phases (Epsilon and Gamma Prime) underneath which is the diffusion zone, and under that, is the core material. The compound layer can be reduced by a two stage process involving a higher process temperature. The danger of this procedure is the potential for nitride netwoprking and the risk of cracking, particularley on sharp corners. The ion nitride process on the other hand uses the same elemental gases of nitrogen and hydrogen, but no catalyst. The process relies on the alsmost infinate variability of nitrogen to hydrogen and vice versa to control the surface metallurgy(depending on the steel analysis). Therefore the surface metallurgy is variable. I am very familiar with the nitriding of both forging and extrusion dies with both gas or ion.
Best Regards to you,
David Pye- Meadvilole, Pennsylvania
Hi Laura,
The temperature is 1000 Celsius degrees? The problem is the generation of a diffusion zone with defects (due to instersticial nitrogen in the structure) which affects the high temperature performance (according with oxidation theoric in metals). This problem you can find it in plasma and gas nitriding. My PhD work is related with high temperature sliding wear on H13 plasma nitrided and plasma nitrided + PAPVD coating.
Marlon Cruz- Caracas, Venezuela
May 24, 2008
Hi,
my question is that we use nitriding with nitrogin and ammonia for H13 steel dies , so what is the possible reasons for overnitiding, then what is the possible reasons for nonbuilding nitridng on the dies.
industrial engineer - Westbank, Nablus City, Israel
October 28, 2008
Dear Plasma Nitriding experts,
Does anyone know the role of Hydrogen in plasma nitriding? I am trying to do a duplex treatment (PN+TiN), but can¡¯t get any wear improvement compare to a pure PVD TiN.
Best,
Amy Gardner
A material science student.
- Destin, Florida
+++++
|
November 14, 2008
the ammonia breaks to give molecular nitrogen.but is molecular nitrogen do take part in the diffusion reaction. Annada Prasad Sahooplating shop employee - Orissa, India March 15, 2009 we are using electropulse plasma nitriding.in this we have to use hydrogen and methane along with nitrogen. can anybody suggest why we have to use both the gases and especially methane. we could not get good hardness and wear resistance after nitriding. myil rajengineer - erode, Tamil Nadu, India May 15, 2009 Hi, anodizing - cairo, egypt August 9, 2010 Hi, - Karachi Sindh Pakistan January 28, 2012 Q. I do Ferritic nitro carburising (Gas Medium Nh3+lpg) process in fluidized bed furnace. I found scale after the process. The scale seems to be around 10 to 15 microns on the surface of the components. - Coimbatore, Tamilnadu, India |