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I'll post back with some case depth survey data. Not coating right now. Sometimes electrolysis nickel with full 24hr 375F bake.

Yeah I got that too. Just noticing that hardness is not following temper temps reliably. 52 HRC is the sweet spot for balance between strength and toughness/ductility. What hardness ranges you getting on your tensiles? I'm in the 53-54 HRC with great mechanicals. So maybe my brittle failures...

Yeah case depth survey probably a good idea on some used parts. Compare them all and see if there's a pattern.

Why 17-7? Why not just use 17-4 H1150. Can buy it off the shelf economically and not worry about any ageing dimension issues. Plus you get essentially guaranteed mechanical properties.

6k!? What is the test scope? 1k to slice and do a simple case depth survey of a couple slices should be more than enough. Do one far away from fracture surface and one right beside. Friction could have heated it up to austenitizing temp and then you end up with brittle surface to fracture and...

Hi all, Have some parts made from 300M. Been doing standard processing per AMS 6419. Tensile specimens come back with good ductility and yield. Issue is recent brittle failures at low stress levels. Potentially impact loaded, but nothing that's very different from normal use. I've been playing...

API spec 7-2 has everything you need. You can find older free copies online.

Yeah a better image would help. Sounds like you just need a gas tight rod seal? A plain o-ring won't work very well. Try out a T-seal. They make them in standard sizes to retrofit standard o-ring grooves. Assuming you designed the rod to a standard size. You should be able to get a perfect seal...

Wondering if anyone has used PEEK for a piston seal on here? Application is for a linear seal. Normal design is a standard slipper seal with o-ring underneath a ring of PTFE to energize. If I replace the PTFE with PEEK it should still work I think. Benefit is increased extrusion resistance and...

I typically get material through a third party distributor like SSA. Mill runs are looking more and more attractive everytime we go to make a batch of parts as the shelves are drying up more and more. To make matters worse, I was just quoted 40 week lead time on 300M rounds from Carpenter. Are...

Guess I'll describe the part and why I'm trying to use plate / rectangular bar instead of round bar. The part is essentially a blade that is much taller than it is wide. The dimensions are roughly 8.25in tall, 2.75in wide and 12in long. It's rough machined to this approx size and then hardened...

Yeah my primary material is 300M since it's a vac melt and have had great results at 220 ksi and up. But when you get to parts over 8 inches in diameter finding material is very difficult. And even if you find it, the price is tough. I know there's vac melt 4340 out there too, but it's almost...

Hey all, Found the answer to my question. Short answer is grain structure is mostly retained from whatever wrought process you started with. Grains don't regrow isotropically. They retain the wrought anisotropy. Reasons being materials science that I don't fully understand. At least I learned...

Let me clarify. If the parts are going through a full quench and temper then aren't the grains completely reformed anyway? So even if you started with an amazing forging where the grains follow the shape of the part perfectly, the benefit of the forging is gone after heat treat as the grains...

Hi all, I'm hoping someone can back me up here. I'm making some extreme stress parts out of 4340 round bar per AMS 6415 (air melt). They are machined in the normalized condition then send for hardening. Tempered at 475F to 50-52 HRC. Tensile tests on some test coupons done with the parts put the...

Will and Ed, Sorry for the late reply. Your advice is well taken. I have a pretty good repore with my heat treaters so I'll be leaning on them heavily. That's why they're the experts right? Marco

Hi all, Utilizing 4330 MOD per AMS 6411. After going through the document I found it odd that a temper temperature was not listed in order to hit the minimum mechanical properties specified. Below I list the heat treatment spelled out in AMS6411H. 3.4.5 Response to Heat Treatment Extracted...

btrueblood, You're right. Meant to say fracture toughness. Good catch.

First up, what is the bending stress calculated to be? How is the part loaded? Sounds like it's clearly a fatigue issue so utilizing an ultra high strength steel tempered to max strength might make the problem worse since you usually sacrifice fatigue life for static strength. Also, you...

Hey all, Just got our tensile test specimens back. Results are great: Average of two test specimens: Yield - 237ksi Ultimate - 280ksi Elongation - 11% Reduction in Area - 36% Hardness - 65 HRC So high five to all of you for helping!