The sustainability of powder metallurgy (PM) is becoming more widely recognized in the industry. This additive manufacturing process produces near-net shape parts, reducing or even eliminating the need for secondary machining, greatly minimizing process scrap and energy consumption. It also produces fewer CO2 emissions than traditional metalworking methods, leaving a more positive impact on the environment.
But this bears the question: are some PM materials even more sustainable than others?
Sintered stainless steel is a specific application of powder metallurgy in which stainless steel powder is compacted into shape and heated in a furnace where the individual particles bond to form durable, corrosion resistant parts. While the process used for stainless steel PM parts is similar to the process used for more common ferrous alloys, the eco-friendly perks are even more noteworthy.
Below, we’ll discuss the sustainability of stainless steel sintering and explore the factors that may make it desirable (or not) for your application.
In short, stainless steel sintering is a sustainable manufacturing process. According to Metal AM Magazine, the recycling loop for stainless steel powder metallurgy is extremely effective, and most powdered stainless steel used in additive manufacturing contains a high concentration of recycled materials.
Aside from the sustainability benefits of sintering and powder metallurgy in general – including minimal waste, reduced need for secondary operations, and reduced emissions – stainless steel as a material is eco-friendly itself. Stainless steel powder is commonly made from recycled materials and is entirely recyclable post-processing. Plus, because of its superior durability and corrosion resistance, stainless parts have a longer service life and leave a smaller impact on the environment.
Now that we know stainless steel sintering is a sustainable practice compared to traditional manufacturing methods, let’s dive deeper into each of its sustainable qualities.
Because it is an additive process, sintering requires only the essential amount of stainless steel powder, and little to no waste is produced.
Compared to older or subtractive manufacturing processes, where metal is removed from a part until the desired shape is achieved, stainless steel sintering is significantly more sustainable.
Since stainless steel sintering creates a near-net shape part with extremely tight tolerances, less secondary machining is required to finalize the piece compared to traditional forging and casting. This conserves energy manufacturers would otherwise use to mill, grind, or drill a part post-processing. Not only that, but this saves manufacturers the cost of labor, time, and machine wear, streamlining the production process and reducing its carbon footprint.
Stainless steel is typically composed of a high percentage of recycled metal. Because of this, stainless steel sintering lessens the need to extract additional alloys to create new parts that are recyclable themselves, creating a more eco-friendly production process. Plus, the finished part is 100% recyclable because it’s made from stainless steel, resulting in a circular production model that sustains itself.
Stainless steel is one of the strongest alloys in terms of tensile and impact strength. This strength combined with the enhanced chemical properties resulting from the sintering process make it even more corrosion-resistant and long-lasting. Not only does a stronger, better performing part require fewer replacements – reducing its carbon footprint – but it can also better endure corrosive environments.
Learn more about stainless steel corrosion resistance in this blog post.
Stainless steel sintering typically takes place at temperatures between 2050-2400°F (2100°F in dissociated ammonia atmosphere for N1-grade stainless steel, and 2350°F in a pure hydrogen atmosphere or in a vacuum for L-grade stainless steel.). The sintering furnace consumes a fair amount of electricity to heat the parts to the required temperature, and the sintering process itself can produce small amounts of carbon gasses as the compaction lubricant is completely burned out of the parts.
Keep in mind, while sintering does have a carbon footprint from its energy consumption and small amount of processing emissions, it tends to be much less energy intensive while producing far less sacrificial material scrap than more traditional methods like forging and casting.
So how can stainless steel sintering be more sustainable? Below are some ways to ensure minimal waste and enhance environmental impact:
While stainless steel sintering is sustainable due to its optimized production process and use of recycled materials, it doesn’t stop there. It's important to work with a manufacturer committed to finding innovative ways to enhance sustainability and reduce waste, and has a closed-loop recycling process in place.
Looking for more information about sinter-based additive manufacturing? You’ve come to the right place. Watch this video from our Lighthouse Video Series about the considerations for sinter-based AM beyond sustainability.