wear rate coefficient 1

[enfield]

Hi there
I have posted before but couldnt get an answer. Desperately need a K valve ( wear co efficient) for Steel upon steel * sae 4140 against Sae 1040 - I not sure of the 1040, I am assuming here.
I need to estimate the waer on a rotating rod

The Hardness of the 4140 is in the region of 131 brinell and a surface texture of N8 .

I just need an approx ansew to know if the design stands a chance.
There is a garranteed star in it !!!!
Stephen

 

[Metalguy]

Hmmm, an offer that's hard to refuse! OK, let's see what we have. Soft 4140 is going to be very similar to soft 1040, and when you rub two similar metals together it's usually bad from a wear standpoint. *If* you were to harden the 4140 the wear of BOTH steels would probably decrease.

Next I'll see if I can find some actual coefficients for you.

 

[enfield]

Thank you
As promised . yes I am terrible like that I know what I mean to say but others and I leave info out its a big problem for me
Yes I had intended to harded the 4140 so I had hard on soft ..would the similar percent carbon have any effect??

Stephen

 

[IFRs]

What are the temperature, pressure, rotational speed and lubricant?

 

[enfield]

That was fast
WOW Temperature is between 20 deg and no more than 40 deg c the pressure 4.3Mpa rotational speed 400 rpm and the lubricant is a grease oil ( ep90 ) mix THAT sometimes penetrates hence calling it a boundry lube prob. the grease mix is a very slap dash arangement.So I am try to judge differing materials and shapes etc

Stephen

 

[Metalguy]

Sorry for the delay, but my best source for wear-related topics is an ASM CD-ROM, and my stupid computer refuses to load it-says something about an NTVDF file not accepting it.

Anyway, as you probably already know wear is usually one of 2 types-adhesive or abrasive. With similar metals you frequently get adhesive wear problems. Dirt in the grease gets you abrasive wear (simple, huh?).

Now, we need to know what diameters are involved here, so the RPM gets meaningful.

I don't think the similar C level of your 2 steels means anything at all. Once you harden the 4140 the C will be distributed in a completely different manner--in fact, nearly all HT of steel can be thought of as an alteration of the way C is distributed!

If you can, consider something like nitriding the surface of the 4140-the harder the surface, the better, and nitrided surfaces seems to slide better than many other surfaces.

 

[enfield]

Thanks for the reply
The formula I am using is depth of wear D equals
( force x Length) divided by ( hb x Area) all mutiplied by K co efficient of wear...

But this wear fiddle factor is very vague and I cannot find any
The nearest I came was bronze on steel at 0.001 to 0.01 x 10to the power of -15

it gives me a wear depth after 1725 hrs of use at 400 rpm
of 2.9mm

Seems a liitle low to me ..

The dia of the shaft is 7.5 mm and it bears against a either a ball bearing OR a rounded shaft of 6mm dia

I want to go with the ball bearing as I can keep the shafts short and any missalignment can be LOst as it were

Once again thanks

Stephen