13BT-RX3

I am planning on having my irons surfaced and found a heat treating company locally that does Nitriding. After talking with him i started thinking about the benefits of having other engine internals Nitrited. I remembered a time many moons ago when i attended Continental powerplant school and the instructor was talking about the treatment of their crankshafts. He went on to say their untreated forged crankshafts had a torsional strength of 96,000lb and by just having them Ion Nitrided that their torsional strength increased to 132,000lb!!! I couldn't believe that a coating that only penetrated .003"-.005" could increase the strength of the crank but he assured me that it was true. Has anyone ever considered having their shafts Nitrided? Are there any downsides that i have not considered? It seems like a cheap alternative to buying an expensive two piece shaft.

Lynn E. Hanover

Don't get me started...........Wrapping an aircraft crank with electrical tape would make it stronger, so nitriding would probably help as well. They have a huge problem with torsional loadings and harmonics due to the massive displacements, low RPM at full throttle, and need for light weight. When you see big counterweights mounted on push in pins with plastic bushings, you know they are having torsional resonance problems.



The Mazda crank has those same problems, any similar system or engine crank does too. However the Mazda crank has such a short throw, and the journal diameter is so big that eash has nearly 100% overlap with its main journal, and so is about the stiffest crank you will ever see. Even then the 4 rotor is about as long a crank as you will see.

Even a longer Mazda crank gets to be less than ideal from the torsional resonence problems, like the Porsche flat 12 cylinder engines, the crank starts to wind up like a rubber band.



The object of gas nitriding is to alter the surface material so as to make it very hard (stable) so as to resist wear. If you look at the ends of the Mazda journals you will notice the blue line all around just about 1/16" below the wear surface. The bearing surfaces are induction hardened and although not quite as had as Nitride, are still as hard as Chinese arithemtic. If you loose the oil film for any reason, the hardening process is of no matter. The crank and bearing is gone...........Nitriding is done in an oven at high temperatures. Some warpage may occur during the process. Check the irons, and lap if required, after the nitriding. Typically, one lapping will not get through the nitride. For a second time it will be required.



Lynn E. Hanover

13BT-RX3

Thanks for the reply Lynn. I am taking the irons to get Ion Nitrided. The process temps are much lower to keep warpage to a minimum. It also does not effect the dimensions or surface finish (supposedly )

To_slow

If you have a junk e shaft, measure the run out on it prior to Nitrating and after, it will warp regardless of there process... Not by much but evident that it is..

To_slow

I had a chance to actually get some real data regarding lapping/grinding the irons with and with out re-nitride. I did some plates for a customer last week lapped+nitride.

Here are the Rockwell readings..



New Mazda plate from the factory no miles on it. RC 38-39



Used plate after lapping /Grinding 2-3 thow deep. RC 21-23



Used plate after lapping/grinding with re-nitride. RC 40



Hope that this helps...

13BT-RX3

Thanks, it's good to know that they can do at least as good a job as the factory. How much warpage are you getting on a set of irons that you have had nitrided?

To_slow

I don't get any, the place that does them for me knows what I want and really does a good job to make sure they don't warp.. The trick is to have them done at the lowest possible heat the heat treating place has.



On other note I have started to check new plates from the factory for warpage, some do come warped from the factory. I have tested about 10 new plates. for warpage. 3 plates out of 10 had no wrpage and the rest had some warpage raging from 1thow to 4 thow...