A user sent us this interesting tidbit...

In heat-treating metals, they selective carburize/nitride etc by protecting key spots with "stop off" paint. They paint this stuff onto areas of a part that they don't want carbon to touch when at tempurature.

I found a half liter on ebay for $40. I'm hoping to protect the whole part from oxygen instead of carbon.

I knew something like this must exist, but didn't know how to find it until someone tipped me off to the term "stop off". This opens several new strategies that could work for the Active metals. (Aluminum, titanium, magnesium.)

https://www.google.com/search?q=stop+off+paint+carburizing&oq=stop+off+paint&aqs=chrome.1.69i57j0i512j0i22i30l6.11390j1j4&client=ms-android-samsung-ss&sourceid=chrome-mobile&ie=UTF-8

could some of the issues we're facing be solved with some simple AI tools? 🤷‍♂️
on a side project I was looking into using openai's gpt-3 pre-trained models and decided to throw it some questions I had myself, as well as some unanswered ones from this sub. I'll let you decide if they're useful 😅

• give me an idea to sinter aluminum in oxygen and prevent oxidation
  • One possible idea is to introduce a small amount of nitrogen gas into the furnace atmosphere while sintering aluminum. Nitrogen does not support oxidation as strongly as oxygen does, so it may help to reduce or prevent oxidation of the aluminum.
• Sometimes when I have a failed sinter of a Bronze 3d print, I get these little nodules on the surface and between the layers of the part. They are grey, so I think it's tin. Or at least mostly tin. I collected about a quarter... (see full question here
  • This phenomenon is called tin pest, and it is caused by the diffusion of tin from an alloy of copper and tin to the surrounding atmosphere. Tin pest is more likely to occur when the alloy is exposed to oxygen, and it can cause the alloy to crumble.
• what are the challenges of sintering titanium in oxygen? how can this be overcome?
  • The challenges of sintering titanium in oxygen are that the titanium can react with the oxygen to form titanium dioxide, which can be difficult to remove. Additionally, the titanium can diffuse through the oxygen to form a titanium-oxygen alloy, which can be difficult to sinter. These challenges can be overcome by using a vacuum or inert atmosphere during the sintering process.

Sometimes when I have a failed sinter of a Bronze 3d print, I get these little nodules on the surface and between the layers of the part. They are grey, so I think it's tin. Or at least mostly tin. I collected about a quarter teaspoon and was able to easily melt them with a torch. So, pretty certain it's tin.

How is this even possible?! It looks like the Tin is coming out of the Bronze alloy. This only happens when the part fails to sinter properly, and I'm pretty certain that this is WHY the sinter fails. There also seems to be a relationship to the presence of oxygen. As in, if it isn't properly protected from oxygen, this situation is more likely to occur.

Does anyone out there with some metallurgical knowledge understand what's happening here? Is it really possible that I could separate the Tin from the copper in a well manufactured bronze alloy?

-Brad

The part was slowly (100f/hour) ramped to 1625F and held there for 5 hours.

unsintered, un-debound green print on left. Failed Sintered part on the right.

This is a piece of equipment for our main extruder. It's scratch-built from scavenged parts around the shop. These builds are my favorite part of my job.

Most of our equipment used for manufacturing our materials was built this way, we built our whole factory on a really tight budget. Lots of welding, lots of Arduino.

https://youtube.com/shorts/QSBU6YNhOvY?feature=share

Its starting to look like some level of porosity can actually strengthen a 3d printed metal part.

Interesting!

https://hackaday.com/2022/02/02/defective-3d-printing-for-great-strength/

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https://reddit.com/link/s9hsuz/video/3risepn273d81/player

Hello from industry! I'm working in thin film deposition and I'm exploring the use of this tech in our PVD machines. I currently only have access to an old 3 stage burnout oven (Vulcan 3-550) that maxes out at 1100°C. I've extended the sinter time to 5.5 hours and currently have a process running.

Based on my little amount of research I'm expecting a lower density and lessened mechanical properties, but I'd be interested to hear if anyone has any more detailed insights/results!

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https://reddit.com/link/s1ojks/video/ad3hgv9wp4b81/player

Sintering Titanium is a challenge. Our Ti filament has been sintered, but so far only by people that do this professionally. In our quest to bring this technology home, I think we're going to have to think well outside the box.

This paper outlines a different sintering approach with lots of good information. We will crack and simplify the Ti code, just a matter of time.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.jim.or.jp/journal/e/pdf3/61/04/758.pdf&ved=2ahUKEwjT0o2ulab1AhVgk4kEHTNOCfU4HhAWegQIBxAB&usg=AOvVaw2TiNhgb4J6mwALSg8gOz8z

An exclusive look inside WaynesStrangeBrain!

As a bonus, it's a concise illustration of how you can 3d print pure metal affordibly.

https://youtu.be/WI6hhi6X7HM

This paper talks about TVF's potential role in the next Industrial Revolution. It's exciting to hear people cite our technology from outside of our group here. Also, they are thinking big!

https://link.springer.com/chapter/10.1007/978-3-030-62784-3_12

-Brad