20CrMnTi and 20Cr2Ni4

[dhouse76]

We have a customer that is requesting either 20CrMnTi or 20Cr2Ni4 as a substitute material for 8620 carburized. The application is a spiral bevel gear set in a heavy truck application. How do I compare these materials? I would expect to get the same surface hardness but what about core properties? Should I compare calculated DI results?

 

[CoryPad]

DI or Jominy hardenability are good ways to compare core hardness between two grades.

 

[dbooker630]

Both of these grades are used primarily in China. You can compare DI results and Jominy traverses to get an idea of core hardness properties. The hardenability of the 20Cr2Ni4 will be higher than 8620, the 20CrMnTi similar to 8620. Your customer should also be willing to pay additional for the increased Nickel content of 20Cr2Ni4 compared to 8620.

 

[tbuelna]

You'll need to compare the properties after heat treat. Due to differences in chemistry, the materials can respond different to the same heat treatment. Even slight changes in heat treatment can produce different results in case and core hardness with the same material. If you are substituting materials, you should adjust your heat treat process to obtain the properties you require.

Since this is a carburized gear application, I'd recommend taking a look at AGMA 923-B05.

 

[dhouse76]

Thanks to everyone for their recommendations. I have found this very helpful.