1084 and 1084-15N20 damascus heat treating problem

J

Jay west

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Jul 9, 2012
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I've run into a perplexing issue which I've been unable (so far) to to deal with. I'm an experienced apprentice bladesmith with good tutoring and have successfully heat treated perhaps 300 blades in my knife making experience. This week I attempted to heat treat 3 small Bowie blades. All are around 8.5" blades. One is ground from 3/16" 1084 steel from a reputable knife supply firm. The other two are 3/16" thick feather pattern damascus ordered from a highly reputable damascus maker in the US. Each blade was rough ground to .035 on the cutting edge. The welds and the pattern in the damascus were perfect. The manufacturer provided the precise steel mix as indicated above. I heat treated as I have done with scores of other 1084 blades, as follows: Evenheat kiln to 1500F; hold for 5 minutes; instant quench in 120 degree (guestimate) canola oil in an ammunition box that holds 16 litres and was 1/2" from full. I agitated the blade continually in a slicing motion so as not to induce warping and there was no warping on any of the blades. Held in the quench for around 20 to 30 seconds and wiped down with a rag. All three blades failed the skate test with a file. The file bit into the metal as if it were mild steel. I knew immediately the heat treat had failed and I was shocked. ' Never had that happen before. I decided to re-treat them and did so. They failed as before. I next took the blades to my tutor who has 30 years of knifemaking experience and we tested one of the blades on his Rockwell tester. This confirmed what I already knew. The result was 32 RHC, the low end of mild steel rating. Next I borrowed his thermometer and probe for the purpose of confirming the reading on my kiln although I knew based on the steel coloration at 1500 that it had to be close. It was very very close to being right on the money. I've tried longer soak times and both lower and higher heat. It seems I've eliminated all the variables except the steel but I have a hard time believing both could be bad. Today I got reading and I see some people go through as many as 3 normalizing cycles prior to heat treating; something I've never done. Will that help? Does anyone out there have any suggestion? I really need to get these blades right. I have a lot of money tied up in two of them and they were to be for my spring shows. Help; please!
 
Some steel comes from the supplier spheroidized. In some cases, you want to run it up over say 1700 to dissolve stuff properly, but I will let others chime in if that is the case with 1084. I have never done a stock removal blade with 1084 or 1084 based damascus, so my stuff always got pretty hot anyway during forging.
 
Yes, at least normalize twice at 1600+, and ideally you need to be doing a full thermal cycle if working with spheriodized damascus.

The other thing you don't mention, is whether you ground away any potentional decarb, although you shouldn't have much if any if you only soaked for 5 minutes. The question though is where you're testing for hardness, and whether that was ground previously to hardening or not. You can't get accurate readings from the bevel, and if your flats or ricasso weren't ground previous to hardening, may have significant decarb on them, especially if they were spheriodized after being surface ground. Decarb areas will read low, or if significant enough, read dead soft. They will also etch less bold.


I always recommend when checking with a file, use the corner of a 3 square file, and if it bites, file in to see how far it keeps biting. Often times, there's 10-20 thou of decarb and it doesn't cut beyond that, and the steel below is hard.


I will make an observation that some small damascus suppliers that mostly make steel for themselves, and forge blades, don't realize the potential for decarb when supplying billets to others, based on their knifemaking techniques. It's an unintentional oversight, but if you're supplying annealed stock, you either need to do the final grinding to thickness after annealing, or make sure the customer is going to remove enough material over the entirety of the knife to get past decarb.


I try to steer my customers away from spheroidized condition stock unless heavy machining is necessary, and prefer to supply my damascus thermal cycled, and stress relieved and softened to final thickness with fine grain, ready to simply be austenized.

Most people don't realize this thermal cycling needs to be done with any annealed stock for optimal performance. Even carbon steel from your industrial supplier.
 
I would take that blade to a 120 grit belt on the grinder and take down the edge at 30-45°. I bet it starts showering sparks after a second or two.
 
Thanks everyone for the suggestions. I have some food for thought here at least. I ran the blades through a full 3 normalization cycle last night and then heat treated the plain 1084 blade with no change in the results. After reading the posts here I tend to believe that what's occurred is a thin layer of decarbonization. Fortunately I still have enough meat left to clean that up without changing my final blade geometry. I'll just have to be super careful when heat treating to avoid warpage or deal with it after quenching. Will experiment with the 1084 blade as I can throw it away if need be without too much pain. The other two; not so much. Sure appreciate the feedback. Regards, Jay
 
I can't tell you how many times I thought my HT failed because of decarb. A quick pass on the grinder or another grit hand sanding it, all was well. Almost every time I "thought" it was a bad HT, this was the case.
 
Javan: You nailed it. I found hard steel not far down. I removed approximately .007 from each side of the 1084 blade. I had lots of meat left to start with as I heat treat fairly thick to avoid warping and then work it down after hardening. I did a 1500F with 5 minute soak time and it came out fine. I then did the other two and they are fine as well. Can't thank you enough man. I learned a lot through this. Decarbonization was something I had read about but not experienced at least to this extent ever before. Had I done my file test as you described I would have been all right but on the flat is was biting and I figured I had a bad heat treat so I repeated it, adding to the problem. I spent a week thinking I might not be able to salvage those two feather pattern Bowies so I'm immensely relieved. Thanks again.
 
Glad it worked out for you Jay. Definitely nobody wants to lose a nice feather.
 
Good thread.

I got a forge this year. I forged out my first knife from a bar of 1084. After heat treat, the file bit.

I thermo cycled it, and repeated.

There was a good amount of decarb I had to get through on the grinder to get to the hardened steel.
 
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