Low(ish) Hardness Results in Damascus and 80CrV2

ScarFoot

ScarFoot

Knifemaker / Craftsman / Service Provider
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Sep 16, 2021
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I finally got access to a hardness tester and checked a few blanks I made today. I made 4 out of Alabama Damascus (5160, 15n20, Ni200) and all tested at 56-57 HRc. I followed the heat treat they had on their website as far as temperatures (1550 & 350) and quenched in Parks 50. I worked to keep my oil at or below 100 degrees and had my tempering oven on and pre-heated and put the blanks in for the first tempering cycle while they were still hot to the touch. I would prefer them to be a little harder than 56-57 HRc but am not sure whether to try heat treating again. Before the internet that was probably hard enough for a knife but now I‘m not sure.
I also tested a blank I had made out of 80CrV2 and it was 56HRc. I heated it at 1525 degrees F, quenched in Parks 50 and ran two tempering cycles around 350-375 degrees(Per “Knife Engineering“). My main thought with this blank is that it has a tapered tang that meets a distal taper so I know the indenter wasn’t meeting it at 90 degrees which most likely impacted the results. I’ve used the same HT process on a couple other knives I‘ve made out of 80CrV2 and they’ve had great edge retention during testing. I’m probably going to go ahead and finish this one since I know my test was somewhat flawed due to geometry and I’ve had good real world results with the same process.
I have a good material testing type oven and run an extra thermocouple so I can confirm the temp the oven is reading out. It holds the set temp within about 5 degrees so I feel like I’m getting accurate temps. I heat one blank out a time and allow 10-12 minutes soak after the oven reaches the set austinitize temp on all of my blanks. The one 1095 blank I made came out at 61 HRc also using “Knife Engineering” temps and we did check the hardness tester with a 62.7 HRc cal block and it gave a result of 62.5 HRc so I know the dial wasn’t stuck on 56…
I need the Pros to give me a little advice on how to proceed. What do y’all think?
 
Devin beat me to it. Damascus can have several issues. One is there may be soft metals like nickel in the mix, and then other is that the layers are not necessarily evenly hard, thus causing the indenter to try and deflect. That will give erroneous readings.

The other is deep decarb. The process of making damascus causes decarb that is left on the layers as they are stacked and re-welded. This is part of what makes the layers stand out. The surface of the final blade may have a fairly deep decarb, too. Just grinding to bright steel is not removing the decarb. I give the blades a test dunk in FC to check that there is no decarb on the blade before testing or finishing. Many of the new folks who say the damascus won't etch or show up is because the blade still has a good layer of decarb on it.

Testing for hardness - The surface to be tested must be ground clean of decarb and scale. The surface tested must be flat and have parallel sides. The surface should be a clean and flat 400 grit finish. You can't accurately test bevels.
 
ScarFoot said:
I also tested a blank I had made out of 80CrV2 and it was 56HRc.
Click to expand...
The answers about Damascus are right on. Sometimes I get Damascus to test hard, other times it will be lower than expected out of quench. For the 80CrV2 you mentioned, make a couple of test coupons and test those before tempering. Check Rc right out of quench, after it's cooled good and the surface is clean ground to nice bright finish.
 
Have you calibrated the tester? It could be reading low

edit: or i can brush up on my reading comprehension :P
 
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Yes we checked cal and it was good. Also file checked it out of quench and it skated like it was very hard. I had no concerns about it out of quench so I was a little surprised it tested a bit low. But, it’s my first time working with Damascus so I really didn‘t know what to expect.
I’ll see if have a few scraps of the 80CrV2 laying around and run them through the same process I used on the one I tested. I’m fairly confident the low number on it is because there wasn‘t a flat on it anywhere to get the indenter perpendicular to.
 
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