Q:
I need a fastener that can withstand frequent sterilization processes at temps to around 400F. I would prefer a polymer if possible. Also the process is pharma related, so the screws would need to be non leaching and may be exposed to low concentrations of chemicals. Any ideas?

A:
For your process, I would recommend PEEK screws. They are an economic solution and will meet all your criteria. PEEK fasteners are usable and strong to 500F. They are often used in pharmaceutical processes for their high purity and are approved by the FDA, USDA, NSF and USP Class VI medical grades are available. PEEK is also ideal for sterilization processes as it is able to withstand various processes including high doses of ionizing radiation. It is also hydrolysis resistance meaning it is resistant to water or steam at high temperatures and pressures- which occurs often in sterilization. PEEK fasteners being resistant to many chemical and temperature stable, this would be a good choice.

Q:  Hello I am researching titanium and C276 hardware for a submerged application in a high chloride (20,000 mg/L) elevated temperature environment (125F). Corrosion resistance is more important than shear or tensile strength in this application.

A: Titanium screws should be a good choice for your application especially Grade 2 if the strength is not an issue. Hastelloy C276 fasteners may also be a good choice as well if your forming a lot of HCl.  In terms of galling, whenever you have similar fasteners tightened on each other there is the possibility for galling. However there are a few great ways to minimize galling depending on your application needs (See the Blog Post:  https://www.extreme-bolt.com/blog/thread-galling-what-is-it-how-to-prevent-it/).

Q: I’m looking for a nut in a large metric size. I know I can’t get it made in this large a size for class 10 steel so I’m hoping you can recommend a material that can be made to an M16 with similar strength.

A: If you are looking for a lightweight nut that has similar strength properties to a class 10 steel nut you should consider titanium grade 5.  Titanium Gr 5 is a high strength grade of titanium that has very similar strength properties to class 10. Additionally the titanium nuts will be roughly 1/2 the weight of the steel nuts.

Q: Currently I’m using screws made of 400 series stainless steel for use in factory machinery that is moving in a circular path creating a centrifugal force.  Our existing bolts are breaking and we’re looking for a bolt with a more rigid type of material that will not break or rush, and has long durability. Ideas?

A: Super Duplex Stainless Steel bolts should do the trick for you. This material will be about 2x strong as the steel you are currently using. It offers 125 ksi ultimate tensile strength and 82 ksi of yield strength. Super Duplex 2507 is also MUCH more corrosion resistant.

Q: I’m in need of  hex head bolts for a gas turbine hot section application. These bolts would need good strength and min. temperature tolerance of 1000 degF. Any suggestions?

A: A286 bolts are an option, but would be on the lower end of these materials in terms of temperature stability. If you wanted a bit more safety margin in the temperature range, you could consider Inconel 625. Finally if you need the ultimate in strength at high temperature you could consider Inconel 718 or Waspaloy. Inconel 718 bolts offer ultimate tensile strength of 210 ksi and Waspaloy bolts 193 ksi. Both are commonly used in gas turbine applications.

You could see a comparative list of high temperature fasteners at https://www.extreme-bolt.com/applications-high-temperature.html

Q: Will Nickel 200 bolts be a good choice for hydrofluoric acid?

A: For aqueous HF, Nickel 200 fasteners offer limited protection. If application requires a metal then you may want to consider Monel 400. Monel 400 bolts are the most resistant option for hydrofluoric acid in all concentrations up to the boiling point. If metals aren’t required, then engineered polymers like PVDF / PTFE fasteners also offer excellent protection to HF.

Q: I am looking for recommendations for fasteners capable of operating under load at 2000C, in a mild vacuum environment. The material can be conductive or insulating just along as it does not react with carbon.

A: For temperatures as high as 2000C, Zirconia ceramic fasteners would be your only option. Zirconia is usable to 2100C. This material will also be non-reactive. Otherwise you would have to have no oxygen present in your atmosphere. If that is the case you may consider tantalum metal fasteners. They are non-reactive but can only be used in an oxygen-free vacuum a those temperatures.