Product Description

The inner bore of wind turbine hydraulic cylinders is typically electroless nickel plated. Our company has developed a QPQ treatment for steel pipes to replace the electroless nickel plating. QPQ stands for Quench-Polish-Quench. It involves placing black metal parts in two different salt baths, allowing multiple elements to infiltrate the metal surface to form a composite infiltration layer, thereby achieving the purpose of surface modification of the parts. It is not quenched, but achieves the effect of surface quenching, hence the name QPQ in foreign countries. In China, it is known as "Nitrogen-Carbon-Oxygen Composite Treatment Technology."
Advantages of QPQ:
Good wear and fatigue resistance
This process enhances the hardness and wear resistance of various black metal parts, reducing the coefficient of friction. Post QPQ treatment, the wear resistance is over 16 times higher than conventional quenching and over 9 times higher than high-frequency quenching on 20# steel, and over 2 times higher than hard chrome plating and tungsten nitriding.
Fatigue tests show that this process can increase the fatigue strength of medium-carbon steel by over 40%, outperforming both ion nitriding and gas nitriding. This process is particularly suitable for complexly shaped parts, addressing technical bottlenecks and easily overcoming deformation challenges.
2. Excellent corrosion resistance
Samples treated with various materials and processes were subjected to continuous spray tests according to the ASTMBH7 standard under identical testing conditions. The salt spray test temperature was 35±2°C, with a relative humidity of >95% and a 5% NaCl solution spray. The test results show that the corrosion resistance of parts treated with QPQ is five times that of 316L stainless steel, 70 times that of hard anodized coating, and 280 times that of black oxide coating.

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