griding cracks on nitrided tool steel
griding cracks on nitrided tool steel
(OP)
I am working on a grinding issue where our H13 nitrided parts are cracking and chipping on a 90 deg internal cylidrical edge. Only around 3-7% of parts will chip, and there are no signs of grinding burn, Any ideas?





RE: griding cracks on nitrided tool steel
RE: griding cracks on nitrided tool steel
If they occur in batches check your wheel size - as you approach stub size your SFPM --you may be getting so slow that your wheel is acting too hard.
Alternatively if you are grinding the shoulder take a look at the dressing of the radius it maybe loading up.
RE: griding cracks on nitrided tool steel
You might want to ascertain if you have a White Case.
What is your nitriding process and conditions?
When you nitride the part how much grinding is needed to bring the part to size?
RE: griding cracks on nitrided tool steel
As for the white case, about 100 microns is removed from the parts on both the shoulder and ID which do not have the white layer removed before grinding, From what I have read is well below the white layer and into the diffusion zone. The nitriding process used is just regular gas nitriding with ammonia I believe, althogh I think i remember someone saying that a batch of plasma nitrided parts was tested once and they all cracked/chipped during machining so I should probably do more research on the difference between the two.
** Would it be advantageous to remove the white layer before grindng, is this the usual process for grinding nitrided parts?
The surface before grinding has cracks in the white layer which under magnification look terrible, I have done some tests and grinding away these cracks usually occurs so they must be superficial and not very deep at all. But I have to wonder if they contribute at all to the chipped parts.
One article i recently read said that nitrided parts should just simply not be ground after processing.
It seems like a complex problem so it must have a simple answer. Have definitely learned a lot about grinding though.
RE: griding cracks on nitrided tool steel