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topic 6157

Plasma Nitriding is not working


We are having a set up, for doing plasma nitriding. We under take different type of jobs like gears, etc. Recently we tried to do the plasma nitriding on a component of ring shape. For volume accumulation we stacked the rings one over the other. After plasma nitriding we find that the top ring gets proper hardness whereas the bottom and pieces stacked in the middle have low hardness. We like to know the reasons. We feel that it may be due to

1. contact of one surface over the other preventing the gas entry or

2. the rings form a hollow shaped tube and the gas is prevented from circulation by the bottom base on which the rings are kept. Virtually the gas are stagnated in the bottom portion.

Please say our views are correct or any other reason exists


Harish Patel
diesel mfg. - Bangalore,India


I am not an expert in ion-nitriding nor have I ever done it. But I know a few things about plasma and these are just comments. I believe the purpose of plasma is to generate and accelerate nitrogen ions and shoot them into the steel (or implant them) which then diffuse to a desired distance depending on temperature. The plasma and temperature both need to be uniform around the part to impart uniform properties. When you stack parts, the plasma may not be uniform around the part. As a matter of fact, there will be no plasma where parts surfaces are in contact with each other.

In a hollow tube, you have a different problem. Depending on the diameter, you may need a separate anode inside the tube to sustain plasma uniformly.

Mandar Sunthankar
- Fort Collins, Colorado



I have many years hands on experience with plasma nitriding and can confirm that you need to space the components apart. The spacing is critical if you are to get uniform nitriding and minimal movement. Also note that any spacers will have to be sufficient in number to support the column if you stack and will not contribute to distortion of the rings. Also, where the spacers touch the rings you will have a "soft Spot" which will not be nitrided at all.

Best Regards

richard buster
Richard Buster
- Wolverhampton, United Kingdom

October 30, 2011

Dear Sir,

The so called soft spot, where two components touch other, does it appears different/visible with eyes, is there a color difference, etc.

With Regards

Maulik Savalia
- Rajkot, Gujarat, India

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