Blade thin mulch lift tearing

[1RB2534]

I removed my blades yesterday off a Cub Cadet 42" (2 blade) deck mower. I'm 72 yrs old and never seen anything like this (prior install and after pics attached). I don't recall hitting anything serious since I put these blades on in the spring when I last sharpened them. After I saw them, I rotated them in place (by hand) to see if they were too long and hitting each other or the deck. But even in the tightest scenario I could still get cardboard between them with no friction. [Edited out line rets]
I didn't notice last spring when I put them on but it's apparent now these blades have a really thin flare on the mulch lift. And it's tearing at the edges and literally coming apart. Anyone else seen anything like this?

This is what the blade looked like when I installed them last spring


And this next one is both blades I removed yesterday.

 

[MParr]

They are worn out. That’s what continuous sand blasting does.

 

[ILENGINE]

And I think you will find that the wear corresponds with a grass buildup ridge under the deck.

 

[1RB2534]

Thanks MPar and ILENGINE, for the replies. At least I understand what it is now. It's been so dry this year there has been areas with exposed sand. I mow an acre and the blades did 2 full seasons and been sharpened twice.
I was just a bit bewildered having never seen anything like that. I have seen blades become so wore the edges curve etc, but never paper thin areas dis-integrating at edges like this. The replacement blades I bought do not have such thin mulch flares so maybe they will hold up better.

By the way, [Edit] I now see the Edit down below so I can take out the line returns I left in my original post. I missed that on the original.

 

[ILENGINE]

Thanks MPar and ILENGINE, for the replies. At least I understand what it is now. It's been so dry this year there has been areas with exposed sand. I mow an acre and the blades did 2 full seasons and been sharpened twice.
I was just a bit bewildered having never seen anything like that. I have seen blades become so wore the edges curve etc, but never paper thin areas dis-integrating at edges like this. The replacement blades I bought do not have such thin mulch flares so maybe they will hold up better.

By the way, [Edit] I now see the Edit down below so I can take out the line returns I left in my original post. I missed that on the original.

Had a customer that lived on a river bluff years ago and had a high sand content in his yard. He would go through 3 sets of blades a year because of similar issues to your blades, and over a 4 year period it actually cut the bottom 1-1/2 off of the deck skirt.

 

[bertsmobile1]

We have just gone into flood but the 3 years previous were drought.
The customers with 1 acre wer doing a set of blades every season and my commercial customers were going through blades at around 3 times the regular rate

 

[MParr]

My dad owned a John Deere D100 with a 42” deck. His lot was one acre and had sandy soil. He would go through two sets of blades a year. I had to replace the deck because the sand blasted two holes in the deck top. There was now way that it could be repaired. That mower is 22 years old and still going. My sister has it now and it’s recently had another deck put on, for the same reasons. It’s been an amazing mower. The 17.5 B&S one banger has never missed a beat.