Why in liquid carburizing mixture of salts is preferred than single salt

In liquid carburizing, a mixture of salts is often preferred over a single salt due to several advantages:

1. Controlled Carbon Potential: A mixture of salts allows for better control over the carbon potential of the carburizing atmosphere. Different salts decompose at different temperatures, releasing carbon in varying amounts. By using a mixture of salts with different decomposition temperatures, the carbon potential can be tailored more precisely to achieve the desired case depth and composition.

2. Uniformity of Carburizing: The use of a mixture of salts can result in a more uniform distribution of carbon within the steel part being carburized. This is because the decomposition of different salts occurs at different rates, leading to a more gradual and controlled release of carbon into the surface of the steel.

3. Reduced Risk of Decarburization: Decarburization, the loss of carbon from the surface of the steel due to oxidation, can be minimized by using a mixture of salts. Some salts in the mixture may act as inhibitors or scavengers for oxygen, helping to protect the steel surface from oxidation and maintain the desired carbon content.

4. Improved Surface Finish: The use of a mixture of salts can contribute to a smoother and more uniform surface finish on the carburized parts. This is because the decomposition products of different salts may have complementary effects on surface roughness and surface chemistry.

5. Enhanced Process Flexibility: A mixture of salts provides greater flexibility in adjusting the carburizing process parameters, such as temperature, time, and atmosphere composition. This allows for optimization of the carburizing process to meet specific requirements for case depth, hardness, microstructure, and surface quality.

Overall, the use of a mixture of salts in liquid carburizing offers greater control, uniformity, and flexibility compared to using a single salt. This can result in improved process performance and quality of carburized parts in various industrial applications, including automotive, aerospace, and machinery manufacturing.