A few months back, I got a call from a manufacturing client I’d worked with for three years—they make commercial ovens for large-scale bakeries, and their production team was in a panic. Their current washer supplier had failed a round of high-heat testing: stainless steel washers that worked fine at room temperature snapped in half when exposed to 425°F for an hour, ruining a batch of custom oven parts and pushing back a key client order. “Can any washers even hold up here?” the client’s production manager asked. That question stuck with me, because it’s one I hear all the time now, as more of our clients push equipment design into hotter, more demanding spaces. As a washer supplier, I don’t just sell parts—I test, troubleshoot, and help clients avoid costly mistakes, so today I’m breaking down whether washers can actually work in high-temperature environments, what works, what doesn’t, and what you need to know before placing your next order. Washers
First, let’s define what we’re even talking about when we say “high-temperature environments.” For most industrial applications, that’s anything above 500°F, right? But wait—actually, that’s a common misconception. The heat a washer is exposed to isn’t just the ambient air temperature around it. A washer clamped between two metal plates in a furnace might see localized spot temperatures of 800°F, while a washer in a boiler exhaust line could cycle between 100°F and 1200°F multiple times an hour. It’s not a one-size-fits-all number, and that’s where most suppliers (and clients) go wrong: they pick a washer material that works at a static high temp, not one that handles thermal cycling, corrosion from heat, or the mechanical load it’s under when tightened.
Let’s start with the most common mistake: assuming 304 stainless steel (the go-to for most general washers) works at high heat. I see this every week. 304 is great for room temp to 700°F static environments, but put it under sustained heat above that, and two things happen. First, its tensile strength drops. At 800°F, 304 loses about 25% of its room-temperature tensile strength. If you’ve torqued a bolt to 50 ft-lbs, that washer, stretched thin by heat, can no longer hold that tension—so the bolt loosens, parts shift, and you get failures. Second, 304 is prone to sensitization at temperatures between 800°F and 1500°F. Sensitization happens when carbon in the steel binds with chromium at grain boundaries, leaving areas with too little chromium to resist corrosion. That’s how a perfectly good-looking washer can crack and break after a few months in a furnace. We had a client in the heat treatment industry last year who learned this the hard way: they switched from 304 to a higher-grade alloy, and their washer failures dropped by 90%.
So what materials do work for high temps? Let’s get specific, because not all high-temperature materials are created equal. For static, non-cycling environments up to 1200°F, 316 stainless steel is a step up from 304, but even that has limits. 316 handles sensitization better (thanks to molybdenum) but starts losing tensile strength at 900°F, so it’s not ideal for anything above that. For temperatures above 1200°F, we move into alloys like Inconel 625, Hastelloy X, and monel. Inconel 625 is our go-to for applications like turbine engines and kiln parts—it maintains 80% of its tensile strength at 1500°F, and resists oxidation even when exposed to hot air for years. Hastelloy X is better if you’re dealing with heat plus corrosive gases, like in chemical processing furnaces or biomass boilers, because it holds up to both high heat and sulfur-based corrosion.
But here’s the thing: material is only half the battle. The form and finish of the washer matter just as much, especially when you’re dealing with thermal cycling. Thermal cycling is when a part heats up and cools down repeatedly—like washers in a power plant boiler that go from room temp to 1100°F every time the plant starts and shuts down. Metals expand when heated, contract when cooled, and if their expansion rates don’t match the bolt and plate they’re clamped to, you get stress fatigue, which leads to cracks and breakage. We test all our high-temperature washers for thermal cycling using a thermal shock chamber—we heat them to 1200°F, drop them into cold water, and repeat 100 times. If a washer cracks during that test, we scrap it and go back to the drawing board. Last year, a solar thermal equipment company came to us with washers that were cracking after 6 months of daily cycling. We tested their original washers (316 stainless) and saw 12 cracks in 50 samples during thermal shock testing. We swapped them for Inconel 718, which has a more matched expansion rate with titanium bolts (the other part they were using), and the failure rate dropped to zero.
Another factor people overlook: load and torque. A washer’s job is twofold: distribute the bolt’s clamping load evenly across the part surface, and act as a barrier to prevent vibration from loosening the bolt. At high temps, metal softens, so you can’t torque a bolt to the same spec you would at room temperature. If you torque a bolt to 100 ft-lbs on a part that’s going to run at 1000°F, that washer will crush, the bolt will stretch too far, and you’ll get a bolt failure. We work with every client to calculate the correct torque spec for their application, using data from thermal tensile strength tests. For example, Inconel 625 washers have a maximum safe torque of 75 ft-lbs at 1000°F, compared to 120 ft-lbs at room temp. That’s not arbitrary—that’s data we collect every day in our testing lab.
Wait, what about non-metallic washers? For really high temps, like above 2000°F, sometimes people reach for ceramic or graphite washers. That’s not a bad call, but again, it’s situational. Ceramic washers hold up to 2500°F, but they’re brittle—if there’s any vibration or movement, they crack. We use ceramic washers for static, low-vibration environments like furnace door seals, but we won’t recommend them for turbine applications where there’s constant movement. Graphite washers are good for temps up to 1800°F, and they’re self-lubricating, which is great for preventing bolt seizing, but they can’t handle mechanical load the way metal washers can, so they’re mostly for sealing, not clamping.
I want to be clear: I’ve seen a lot of misinformation online about high-temperature washers. Some suppliers will sell you a “high-temperature stainless steel washer” that’s just 316, and call it a day. That’s risky, because 316 fails above 900°F. Last quarter, we had a client from a food processing plant who bought cheap “high temp” washers from a big box industrial supplier, only to have them fail during a pasteurization process that ran at 950°F. The washers disintegrated, metal shavings got into the food, and they had to recall 20,000 pounds of product. That’s the kind of disaster we work to prevent. As a washer supplier, my job isn’t to sell the most expensive part—it’s to sell the right part for your specific heat conditions, load, and cycling.
Let’s talk about a recent success story to put this all in context. We had a client that makes components for nuclear reactor cooling systems. Their original washers were 304 stainless, and they were failing after just 3 months in temperatures up to 1100°F, plus constant exposure to coolant corrosion. We tested their application, recommended a mix of Inconel 600 washers for the high-heat areas and Hastelloy C-276 for the areas with more coolant exposure, adjusted their torque specs, and added a dry film lubricant coating to prevent seizing during installation. They’ve been running that setup for 18 months now, zero washer failures, and their maintenance costs for that part have dropped by 70%. That’s the kind of result that matters, not just spec sheets.
So to circle back to the original question: Can washers be used in high-temperature environments? The short answer is yes, but only if you pick the right material, consider thermal cycling and load, and work with a supplier that does rigorous testing. The mistake most people make is thinking all high-temperature materials are the same, or that a material that works at static high temps will work when you heat and cool it repeatedly. That’s where experience matters. Over the past 12 years as a washer supplier, I’ve tested hundreds of materials, worked with clients across industries from aerospace to food production, and I can tell you there’s no one-size-fits-all solution.
Bolts If you’re working on a project with high temperatures—whether it’s a furnace, turbine, boiler, or industrial oven—and you’re not sure what washers to use, don’t guess. A wrong choice can cost you thousands in damaged parts, downtime, or even safety hazards. We specialize in custom washer solutions for high-temperature environments, and we’re happy to run free testing on your specific application materials to find the right fit. If you need help troubleshooting current washer failures, or want to get a quote for custom high-temperature washers, reach out to our team to start a conversation. We’ll walk you through every step, from material selection to torque specs, so you don’t have to learn the hard way like so many of our clients did.
References
- ASM International. (2007). Properties of Stainless Steels and Nickel Alloys for High-Temperature Applications. Materials Park, OH: ASM International.
- NASA. (2012). Materials Selection for High-Temperature Aerospace Components. NASA Technical Report TP-2012-217234.
- Industrial Heating Society. (2019). Guide to High-Temperature Fastener and Washer Selection for Furnace Systems. The Journal of Industrial Heating, 86(3), 45-52.
- International Organization for Standardization. (2015). ISO 3650: Metallic Washers for High-Temperature Applications. Geneva, Switzerland: ISO.
Handan Jihao Fastener Co., Ltd.
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