Lionsteel M7 and Sleipner steel





Ok here are my views from using the Lionsteel M7 for 2 weeks solid in the field. Just to set the picture of the testing grounds. The river is flooding and broken it's banks only 200m from where I'm sitting in this small village with dirt roads and where the locals still use horse and carts-ok get the picture. It's wet and wild.

I've got to say that I think Uddeholm Sleipner is not as good for knives as D2. It's use for outdoor knives is a secondary function in terms of it's original applications, ie in the tooling industry. For a start my Kizlyar Supreme Maximus made from D2 does not suffer from the rusting like the Sleipner. Yes, I know Sleipner has even less Chromium (Cr) than D2, quite a lot less. My D2 blade has never chipped but my Sleipner alloy blade of the M7 has multiple chips from some rather light work, in fact more chips than my Cudeman 299B made from Bohler's N695, ie 440C steel!.Sleipner is supposed to be better at resisting chipping than D2 under equivalent conditions.
The blade of the M7 I have was pitted within minutes of use. I crossed a river on foot which took about 2 minutes to travel about 20m or 60ft (it was almost waist deep and flowing very fast). I did some lightweight chopping and some food gathering (cutting).

The tip of the blade was submerged for about 2 minutes during the river crossing. 

By the way the liquid you see on the blade is NOT water but sunflower oil.

What did Uddeholm say? No reply so far or acknowledgment of my email.

Now a cold fast flowing river in flood is going to contain lots of dissolved oxygen and dissolved salts as well. if the metal is susceptible to pitting it's possible to happen. ie corrosive pitting-IF there are sub-surface, surface defects, and/or impurities within the steel close to the surface. BTW I didn't make this up Google corrosive pitting read the relevant papers, I did.

Is this acceptable for such a knife? Is this a fault of knife manufacture or is this a raw product fault? ie the starting product from Uddeholm was at fault to begin with? Is it a fault at all??

Well if I was in the business of making tools from the Sleipner alloy for it's intended purpose, I might also PVD them, in which case this ceramic nitride coating will help protect the surface from corrosion. BUT I may not PVD them and so would be disappointed if I saw this happening to my tools.

Certainly observation of blade surface by an unaided eye, it was smooth and clean- LionSteel's satin finish! But of course things can change during heat treatment if not done correctly. One side of the blade is not so badly affected. Corrosive pitting effect can be a problem if left unchecked. Small holes can enlarge in all directions, into and away from the initial site weakening a structure.

Here are some macro images of the corrosion. What we see here is a classic example of pitting corrosion where the corrosion is localized, forming pits on the surface. Unlike the type corrosion seen, for example on a basic carbon steel, where the corrosion would be more evenly distributed.

Click on image to enlarge

Corrosive pitting is a real problem when it occurs on the blade as it can significantly weaken it's structure if left unattended or unnoticed. You may not see the pit as the brown stain from iron oxides can obscure the actual pits and corrosive forces will continue.

Protecting from oxygen is one way to deal with this but corrosion need not occur only via  oxygen exposure.

In an earlier blog I said the M7 IS NOT for coastal camping and I stick by this unless you have plenty of fresh water to wash it off immediately then you will have lots of rusting.

Any outdoor use knife is exactly what the name implies, it should be good for outdoor use and that means occasional subjection to liquid water, water vapour, dirt, blood and guts and other animal products, potentially corrosive plant saps (there are many, did you know this?), sweat (contains salt NaCl!), salted meats, and plant acids (fruits).

Since this M7 blade did not corrode all over I'm going to suggest that this pitting seen is a defect in the overall homogeneity of the alloy.


Again I want to know what Uddeholm has to say, ie is this normal or abnormal.

If you have read this far then you will now know that a link to this blog has been posted on Blade forums as well in the LionSteel manufacturers area.

Of course once the steel leaves Uddeholm then the heat treatment is not there responsibility, it's the responsibility of the (in this case) the knife manufacturer.

Camping or working around rivers can be tough on a knife, almost everything you cut near water level or material that has been previously submerged will be abrasive (containing mineral particles from silts etc) if the river is prone to flooding. That means collecting herbs for tea making, chopping wood or carving woods that were previously submerged can be abrasive on a blade cutting edge and general faces of the blade. So the last thing I want is to see corrosion like this occurring on or near the cutting edge.



Remember the Lionsteel M7 is NOT guaranteed against anything except cutting tasks and manufacturing defects.


More to come stay tuned!


Ok here is what Uddeholm had to say re the images:

"Looking at the photos I do not see the corrosion as something unexpected. Neither Sleipner or D2 are corrosion resistant steel grades and are considered to have a similar behavior in contact with water. The lower Cr content of Sleipner compared with D2 does not affect the corrosion resistance in any significant way since it is the Cr content in solution in the base steel that determines that. You cannot just look at the Cr content of a steel to determine how corrosion resistant it will be. You have to take into account also the carbon (C) content and other alloying elements. In both D2 and Sleipner almost all the Cr is tied up in the carbides that give the steel its wear resistance. In D2 you have both a larger Cr and C content, ~12% and 1,5% respectively, which result in more carbides in D2 than in Sleipner with ~8 % Cr and 0,9 % C. But both have approximately the same amount of Cr remaining in solution. However, what is left in solution in both grades is much less than the minimum of 12 % Cr in solution required for a corrosion resistant steel. Compare with our Elmax which has 18 % Cr + (3 % V and 1 % Mo) to react with the 1,7% C to achieve more than 12 % Cr left in the base steel and become corrosion resistant.

The extent of corrosion here is perhaps a little worse than I would expect after only a few minutes in water but the extent of attack is also affected by other factors like for example the surface finish and how the steel has been heat treated. In this case it seemed like the surface finish of the knife in the photo was a little rough aside from the grinding which could have contributed to the fast attack. It could also be due to the heat treatment since that will affect both Cr content in solution and also how the carbides are distributed which can in turn affect the speed of the corrosion attack."

Ok Ok I forgot the Cr in solution-pretty dumb of me and careless but........
Let's clean up the blade now with metal polish and see what happens over the coming weeks use. Stay tuned!