316 vs 17-4

MaxPrairie · Jul 31, 2015

I've got a reoccurring order to repair some parts that wear out. The part is roughly 5/8" sqaure and gets welded to a 316 shaft. Currently we are making the part out of 316 (which is what the original piece was) but seem to be wearing out faster than the original. I have certs on all stainless and all checks good. I'm wondering if I should try some 17-4 H1150 and see what happens? I'm thinking machine the part after heat treatment. The part will be welded to the 316 shaft and with no filler metal.

Am I just creating more problems for myself here? Is the welding going to mess up the heat treat? Corrosion resistance is a big deal here also, how does the 17-4 compare? :eek:

Bobw · Jul 31, 2015

17-4 or 316... That's like being given the choice of aluminum or inconel...

I have no idea what the welding will do... I'd almost offer to make the shafts out of 17-4 for free just so
I wouldn't have to deal with the 316... I thought I hated 304 until I worked with 316... And I thought
I hated 316 until I worked with 321... I'll take Ti, A286, Inconel, Aluminum Bronze, Waspalloy over 304/316/321
any day of the week. I hate 300 series stainless... Except 303.. "304 she's a whore, 303, she's for me."

As for wear resistance on the 316... I was recently forced to learn a bit about shot peening.. You may be
able to effectively case harden the surface after welding by shot peening.. (sand blasting, but with
little steel balls)

A dry film lubricant might help possibly also...

Mtndew · Jul 31, 2015

17-4 is easier to machine than 316.

JS · Jul 31, 2015

Make the whole thing from Nitronic 50...
We use it in the mine's vertical and horizontal acid pumps. 300 series doesn't last as long as the Nitronic...

vanguard machine · Jul 31, 2015

i really don't get the hate over 3 series. i guess i had to learn to love the stuff since i do so much marine related stuff.
it welds like a dream and with the proper tool geometry and coolant machining isn't so bad..tapping the stuff however..ughhhh

Bobw · Jul 31, 2015

vanguard cycle said:
i really don't get the hate over 3 series. i guess i had to learn to love the stuff since i do so much marine related stuff.
it welds like a dream and with the proper tool geometry and coolant machining isn't so bad..tapping the stuff however..ughhhh

Its what you do and what you are comfortable with it... I hate it, I don't deal with it much, 300 series makes me unhappy. I'm also
not very comfortable machining aluminum, and that is supposed to be the easy stuff.

MaxPrairie · Jul 31, 2015

We machine lots of 304 and 316, not so much 303 unfortunately. The welding is more of what I'm unsure of than anything else. From what I've read 17-4 to 316 shouldn't be an issue, but this is just coming from a quick search. Anyone have any experience or see any trouble here?

adama · Jul 31, 2015

FYI, start in a shop that machines alu and 304 will make you cry like a baby. After machining high magnese wear plate 304 and 316 is like cutting leaded steels :-) All depends on what your use too and how good a grasp you have on the basics of actually cutting metal not pushing it out of the way, because that’s the difference between it being hard or easy in the 300 series stainless range :-)

If the parts are just 5/8" square and you don't have do do too much with them, you could go look at some of the far higher spec alloys, like the inconels. Yeah there way more costly, but at that kinda size depending on the work in the part that cost really might not matter much for a massive life increase. Worst case you may have to switch from a fusion weld to one with filler to get the weld to work well, but that probably is not too much of a issue.

You need to also factor in if the heat from the welds going to be affecting the materials properties, if so you might need post weld heat treat which can cause intergranualr corrosion to happen on certain stainless alloys if done at the wrong temps.

JS · Aug 1, 2015

It's funny I cut my teeth on 416, and 300 series, 304, 316, 17-4 when I started this trade. After almost a decade of pump manufacturing. I actually thought it was easy after a while.

Orange Vise · Aug 1, 2015

Austenitic stainless steels (nonmagnetic, non heat treatable) like 304 and 316 generally aren't used interchangeably with martensitic, precipitation-hardening grades (magnetic, heat treatable) like 17-4.

And yes, the welding will mess with the material properties.

What are these parts for? Why was 316 originally specified? The corrosion resistance of 316 is tough to beat. JS' recommendation for Nitronic is a good one. It's austenitic and frequently used when higher strength is required. However, $$$...

MaxPrairie · Aug 1, 2015

316 for food grade. We only repair, original manufacturer's spec is 316.

SND · Aug 2, 2015

Sounds like its a Tig fusion weld, usually shouldn't be much of an issue between the 2. Heck I weld big 625inco and C-276 to 316 for pressure vessels...

I'm not sure if it would do much for your wear resistance.

Bobw · Aug 2, 2015

Just a thought... Something in a system always has to wear out first, or break first... If designed well
the thing to wear or break first is relatively cheap and easy to replace...

By increasing wear resistance on this one part, are you then going to wear out a much more expensive part of the system,
one that is not so easily replaced?

PlasmaOnTheBrain · Aug 2, 2015

You are going to need some sort of filler metal if you want to weld the 2 together. It can be done but not without alloy additions from the filler wire...

qrovin · Aug 3, 2015

Small diameter blind holes or cutting long id parts on stainless is just so much fun.
Make the material poor quality stainless and that brightens your day even more.

For dessert try tapping deep small diameter blind holes like 8-32 and smaller .

Lovely time ,

MaxPrairie · Aug 3, 2015

I made this thread to get your guys' thoughts on the issue. Bill, if I went through with the change I would make sure to cover my ass. This part is the most difficult to replace, the other takes about 30 seconds to remove and replace. I will be showing this to my welder in the next day or two to see his thoughts again.

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