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- Dec 11, 2000
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A question for the metallurgists. Other than picric acid, is there any way that I can bring up the prior-austenite grain boundaries in martensitic steel? That is assuming that I am right that picric acid is the usual way of doing this? I had been hoping to measure grain size, but not being a metallurgist I was unaware that nital (the etchant my company uses for everything else) wouldnt provide this information.
In the present climate I would not expect to make much progress obtaining picric acid.
With a nital etch, and the aim to improve my heat treating, what should I be looking at? I made a number of samples from a small bar of O-1 steel, no grinding or forging, just thermal cycles. When broken there was a visible difference between the sample that had been heated and quenched once, and one that had been normalised three times in air, fast normalised twice more in oil, then final quenched. At 1000x though, to my untrained eye, there was little to differentiate between them. There was a greater difference at 400x where the harder, finer sample showed a more uniform dark color and the single quench sample showed many pale blotches.
I have already learned from making these samples. Cycling clearly makes for a finer structure, as seen at the break. Soaking at non-magnetic made for a harder sample than only a brief time at non-magnetic. Full hardness is only attained some time after the steel reaches room temperature, even cold to the touch after quench the steel remains ductile. That is all good information, but I really want quantify what is happening in the steel.
Hope I am not barking up completely the wrong tree.
Thanks
Chris
In the present climate I would not expect to make much progress obtaining picric acid.
With a nital etch, and the aim to improve my heat treating, what should I be looking at? I made a number of samples from a small bar of O-1 steel, no grinding or forging, just thermal cycles. When broken there was a visible difference between the sample that had been heated and quenched once, and one that had been normalised three times in air, fast normalised twice more in oil, then final quenched. At 1000x though, to my untrained eye, there was little to differentiate between them. There was a greater difference at 400x where the harder, finer sample showed a more uniform dark color and the single quench sample showed many pale blotches.
I have already learned from making these samples. Cycling clearly makes for a finer structure, as seen at the break. Soaking at non-magnetic made for a harder sample than only a brief time at non-magnetic. Full hardness is only attained some time after the steel reaches room temperature, even cold to the touch after quench the steel remains ductile. That is all good information, but I really want quantify what is happening in the steel.
Hope I am not barking up completely the wrong tree.
Thanks
Chris
