As today’s engines develop towards high power, low energy consumption and long life, valve seats, as important engine components, have further strengthened performance requirements.
You might know that each engine cylinder has an intake and an exhaust valve, each with a valve seat.
In China, the total annual sales of valve seats is about 650-800 million.
Valve seat absorbs the high-speed impact of the valve while providing a durable, heat-resistant surface that ensures tight seal for valves.
This sealing keeps the combustion chamber airtight, which is essential for efficient engine operation.
The exhaust valve seats also conduct heat away from the cylinder head.
Engine valve seat operates in a very harsh environment, enduring high-impact loads from the valve and exposure to corrosive gases and high temperatures.
The working temperature of a valve seat is extremely high, ranging from 200–450°C for intake valves and 500–800°C for exhaust valves.
Such high temperatures reduce the hardness of the valve seat, causing it to deform and wear out more quickly.
Intake valve seats are exposed to high-temperature oxidizing gases, whereas exhaust valves face high-temperature gas erosion, sulfidation, and oxidation.
Valve seats endure repeated impacts from the valve. In some large engines, the impact frequency exceeds 1,000 times per minute.
For valve seats, you can choose from the following materials: powder metallurgy materials, cast iron, forged steel, or ceramic.
Powder metal valve seats have become increasingly popular due to their cost advantages in mass production, fewer processes, and flexible material design.
However, compared to forged ones, sintered valve seats contain internal pores, decreasing their corrosion resistance and strength.
By utilizing processes such as re-pressing and re-sintering, powder forging, or copper infiltration, the density of the valve seat can be increased to over 7.6 g/cm³, significantly enhancing its performance.
Low-alloy cast iron material is suitable for low-load engine valve seats, as its operating temperature is relatively low. However, high-load engines operate at higher temperatures and in more corrosive environments. Therefore, you should add alloying elements like Cr, Ni, Co, and Mo to the cast iron. These elements will greatly boost the valve seat’s resistance to high temperatures, wear, and corrosion.
Ceramics have excellent high temperature resistance, wear resistance, and corrosion resistance, and are ideal valve seat materials. Yet, ceramics are difficult to process and have high fabrication costs.
The manufacturing process of powder metallurgy iron-based valve seat includes powder mixing, pressing, sintering, copper infiltration, etc.
Mixing combines different metal powders with lubricants and graphite powder. Lubricants improve the fluidity of metal powders and reduce mold wear, while graphite enhances the mechanical properties of sintered parts.
Upper and lower punches press the mixed powders into the mold cavity under high pressure. The pressed powder metal valve seat, called the “green compact,” requires further processing.
Sintering heats the green compact below the metal’s melting point. For iron-based valve seats, the sintering temperature typically reaches 1120 °C. This process bonds the powder particles, giving the valve seat structural integrity, mechanical properties, and physical properties.
Copper infiltration fills the interconnected pores of powder metallurgy parts with molten copper through capillary action. Copper-infiltrated valve seats achieve a density of 7.6 g/cm³ and a hardness exceeding 30 HRC.
Conventional cast or forged alloy valve seat inserts often wear out prematurely and fail. It is economically and technically advantageous to produce valve seats through powder metallurgy.
PM has greater materials design flexibility. For example, the addition of alloying elements to iron-based powder metallurgy valve seats enhances their high temperature resistance, wear resistance and rust resistance.
These high-alloy sintered valve seats can be applied to high-power gas engines and diesel engines.
Powder metallurgy is a near-net-shape manufacturing process with a material utilization rate of up to 95%, effectively lowering the production cost of valve seats.
Sintered valve seats provide cost advantages due to less material waste, fewer processing steps, and lower energy consumption in mass production.
The powder metallurgy process allows stable manufacturing control, resulting in high quality consistency across different batches.
The tolerance of sintered valve seat is generally IT8-IT9, and after the sizing process, it can reach IT5-IT7.
BLUE is ISO 9001:2015 certified, with 20 years of experience in powder metallurgy design and manufacturing – your reliable PM manufacturer.
We supply a wide range of standard sintered parts, including shock absorber components, oil pump gears, water pump pulleys & flanges, standard sprockets, jaw couplings, bevel gears, spur gears, and helical gears.
These standard parts come with no tooling fees.
Browse our standard parts shop to find the same parts for your project.
Assembly failure
Due to improper assembly or excessive tolerance of the valve seat, eccentric wear occurs, which leads to valve seat fracture.
Wear failure
The valve seat is exposed to high temperatures for extended periods, which decreases its hardness and causes it to deform.
Corrosion failure
The exhaust gas discharged by the engine contains corrosive media, which makes the seat surface no longer smooth, increases the friction factor, and intensifies wear.
Iron-based powder metallurgy valve seats sintered at 1120°C achieve a density of about 7.5 g/cm³, a hardness of 86 HRB, and a crushing strength of 220 MPa.
When sintered at 1150°C, the density increases to 7.6 g/cm³, the hardness improves to 92 HRB, and the crushing strength rises to 300 MPa.
Sizing in powder metallurgy is a secondary operation performed on sintered components to achieve tighter tolerances.
After sintering, powder metal parts may undergo slight dimensional changes due to shrinkage or distortion.
Sizing corrects these deviations by re-press the sintered part into the die.
Powder metallurgy sintering is a manufacturing process in which green compacts are heated to a temperature below their melting point in a controlled atmosphere.
The heat causes the metal particles to bond, reducing porosity and increasing density.
This fusion imparts structural integrity and enhances the material’s mechanical properties, resulting in a strong and durable final product…
Powder metallurgy process is a metal-forming method that presses metal powders and sinters green compacts below their melting points to create the final component.
It is a near-net-shape process, allowing the production of complex geometries and intricate features…
BLUE focuses on providing standard powder metallurgy parts without paying mold fees, manufactured in China and serving customers worldwide.
Get a free sample to test before placing an order!
Email: info@powdermetallurgy.com
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