Exhaust valves must withstand high temperatures and pressures, which is why they are made from what material?

Exhaust valves are critical components in an engine that operate under extreme conditions, including high temperatures and pressures. The correct material used for exhaust valves is silicon-chromium steel or alloys containing nickel and chromium.

This is because silicon-chromium steel and these specific alloys exhibit excellent heat resistance, strength, and durability, which are essential properties for handling the thermal stress generated during engine operation. These materials also possess a high resistance to corrosion and oxidation, which is crucial in the combustion environment where gases and other products can be extremely corrosive.

In contrast, regular steel lacks the necessary heat and corrosion resistance, making it unsuitable for exhaust valves. Polymer composites and high tensile plastics do not possess the requisite strength and thermal stability needed for such high-stress applications in an engine, which further reinforces why silicon-chromium steel and alloys with nickel/chromium are the appropriate choice for manufacturing exhaust valves.