Out of my own curiosity, I wanted to see how our printed stainless steel compared to common production stainless steel like 304. I took a few samples to a friends shop and talked about what I wanted to do and off we went. First, 304 is probably one of the most common general use steels made and used in industry. 17-4 is a bit more specialized but its most sought-after features are its high strength and corrosion resistance. This is due to its makeup of about 15% Chromium, 5% copper, and 5% nickel. The high chromium content generally makes this type of metal more difficult to machine as it will gall up and clog cutters, drills, stones, etc. if you run it too hot and without lubrication. Knowing this, I wanted to test it head to head and treat it like 304. The biggest variable is that this is 3D printed metal, not production.
The first thing to do was to fix the part up in an end mill and see how it drilled and what the surface finish of the hole looked like. The material drilled smooth, no chattering, even with no lubrication. It revealed the layering but also smoothed the layers out as the bit pushed through. No real feel difference from the 304.
While fixed in the end mill it was decided to see how it cut with a mill. The part was sidecut and the top edge was surfaced with the mill. Again, with no lubrication, there was no chatter and a nice smooth cut revealing some very minor layering underneath.
The sample was then cut with a band saw. The performance was similar to the drill press test. Unfortunately, I don’t have a picture of it before. It was then welded back up to see how it would fill in. Nothing surprising came of the cutting but the welding revealed some interesting results. This gap was filled in without a rod, just using a tig torch to heat the area and backfill on itself.
Using the same method but with a piece of aluminum under it, a spot weld was applied. It looked great and performed very well here with no impurities showing up on either side.
It was time to lay some filler rod on top at a few different amperages to see how it reacted. We had to go lower than expected but it took the weld without issue.
Lastly, this piece was welded to a piece of 304 edge to edge with no prep to either piece. Once finish welded it was put in a vise and using pliers rocked back and forth till something broke. In this test you do not want the weld to fail, the weld should be stronger than the material it is attached to. And that’s exactly what we got after a few pulls the printed material tore off leaving the weld intact.
My takeaway: I was highly impressed with it and cant wait to experiment more with real parts, having them machined and welded for real world applications. Here are a few more overall shots of the sample part we used. Note that the sample doesn’t have a solid infill which would give us even better results in these types of tests.
A big thank you to Lou from Kaman Tool Corporation in Chicago for taking the time to do this and let me know his thoughts on each of the processes.
Tech Lead – Field Service
Computer Aided Technology, LLC