What is your feeling on using 17-4-PH as a shaft material for pumps or compressors? Has anyone had any problems (vibration problems or otherwise) with shafts made of this material? I'm doing a bit of a reality check here, so any input would be appriciated.

17-4 & 15-5 PH has been used in many critical applications such as Polyethylene Loop Reactor pumps for many years with no problems. All of our Bingham and Lawrence main reactor pumps used 17-4 condition 900.
These shafts were about 3-4" Dia. 6-7' long.

I can't speak as far as Centrifical applications, all of our recip's used 4140 or 4340 Rods with some type of coating like tungsten Carbide.

I used to machine alot of 17-4 & 15-5 for pump shaft material back in the mid to late 90's, most of the time they would specify Condition 900 Hardening.
We Liked it because we could machine it to size and then Condition (Heat treat) it with little or no warping of the finished product. Only thing needed after heat treating was to put it back in the lathe and polish the discolorozation off.

I personally think it's some good stuff.

Later, Jason

17-4 Precip hardening ferritic stainless is used fairly commonly in pump shaft applications, particularly where one needs reasonably good corrosion/erosion resistance, high levels of hardenability and mechanical strength, and has limited space in which to acheive same. I have seen it used many times to replace softer stuff in demanding applications. It was the answer in one case I am familiar with wherein a major mfr had a repetitive shaft failure issue on double suction pumps (fatigue failure right under the impellers) and 17-4 as a replacement for 1045 saved the day.

If corrosion is not an issue (if you don't need the "stainlessness") then 4130 or 4340 can be hardened to similar values and cost less. Austenitics (non magnetic stainlesses like the 300 series) are in many cases better in terms of corrosion resistance, but nowhere near as strong...

I think (if my feeble mind recalls correctly) that you can get upwards of 170Kpsi with 17-4 with proper heat treat.....almost three times the strength of 300 series stainless.....

I have had several instances over the years of pumps or compressors with 17-4-PH shafts experiencing high vibration due to strange rotor bows and rubs. I guess I am trying to determine if thermal instability is a characteristic of this material. I know all the old guys in our organization don't like to use 17-4-PH for shafts in any application and I guess I am pretty wary of it myself, so I am looking if my experience is unique. Sounds like it is.

You may want to have a look at Wilfley Pumps.

They make a very good pump and have material specs you may be interested in.

Stainless steels in general have lower thermal conductivity and greater thermal expansion than regular steel, which make them extra vulnerable to distortion during welding or rubbing. A propensity to gall adds to those effects too,

I found the following quote in EPRI 104213 - Bolted Joint Maintenance and Application Guide - Section 4.4.2 - Inspections due to questionable bolt quality.

"During assembly and subsequent operation questions have arisen regarding material pedigree and physical condition. For some alloys (e.g. preciptation hardening alloys such as 17-4 PH) material property changes due to secondary aging effects can occur."

You be the judge on what they're trying to say (what is a secondary aging effect? What changes in material properties?) and whether this discussion of bolt material is relevant to your question on shafts. If you would like clarification on this quote, you might try to contact the authors - Mike Looram and Edwin Merrick at Aptech Engineering Services, Houston Texas.

Steven,
Steels containing high percentage of chromium and in particular 17-4 PH steels are reported to be highly susceptible to Wire Wool or Black Scab type of babbit bearing failure.I have a few reference articles on wirewool type of bearing damage and the effect of chrome content in shaft material.I can scan and e-mail them if you are interested.<thomas_purackal@pic.com.kw>

Interesting comment about the old timers (like me...... ) not liking 17-4 due to odd behavior. I haven't personally experienced this, but that doesn't mean that it isn't real.....the comments that Dan and EPete make are absolutely true ..... stainless ain't a free lunch. With respect to the galling issue, anybody who has built stainless rotor pumps/compressors, be the material austenitic or ferritic, knows this problem well. It has been my experience that most of the mysterious bows/looseness issues can be traced to galled impeller locknuts (you thought it was tight, but in reality it was galled), etc.....and when that occurs on sleeves, locking sleeves, etc., dynamite won't cause them to release and behave correctly. And if you think the stainlesses are bad, wait til you try titanium/titanium alloys......it will gall in a heartbeat, and once that happens, it might as well be welded......and yes, the expansion coefficient for stainless steels (particularly austentic 300 series is about 1.5 times carbon steel, and if that is not taken into account with respect to assembly tolerances and expected operating temperatures, then mayhem may ensue......

Non-uniform heat treat is a more realistic probability with ferritic stainless than with austenitics ---- austenitics do not appreciably harden, but ferritics obviously do, and if not done properly, then widely varying hardnesses and ductilities within a part can result....

Just out of curiosity, why was 17-4 put forward in the first place - what is it to replace ??

The bulk of my experience with 17-4 PH pump rotating elements has been in CO2 scrubbing services - Benfield Solution circ pumps (ammonia and methanol plants) and in steam reform hydrogen plants wherein the pumped fluid was DEA/MEA. In both cases, the pumping environment was a gas-saturated aggressive fluid, and 300 series stuff would stand up well to the corrosion environment, but would be massacred by the flashing/cavitation of the CO2-saturated solutions.......the 300 series simply were not hard enough to resist the cavitation/flashing.

Interested to hear more.......

This message has been edited. Last edited by: DRainey,

Revise the previously revised revision.....

17-4 DOES NOT have a coefficient of thermal expansion significantly different from garden variety carbon steels......it is about 6.0/6.2; it is the austenitics (non magnetic stainlesses) that have the high expansion coefficient.......

sorry -

My current problem is a compressor shaft made of 17-4-PH. This material was selected in the original design for corrosian resistance. The process has some strange cats and dogs in it that like to eat 4140 under the right conditions. Anyway, I have one rotor that has worked fine for years, everytime I put in the spare I get 4.5 mil pp on a 8700 rpm compressor. Not good. The first time it happened we thought it was just a bad shaft. We pulled out the spare,put the original back in, and eventually we scrapped the shaft, had a new one built, and when we put it in on this last turnaround, had the same problem.