Selection of Material for Tappets

[qsexp]

Hi,

One of my customers has raised an enquiry for mechanical Tappets for a multi cylinders passenger car engine

Can anyone advise us on relative advantages of Tappets manufactured by the Chilled Iron route Versus Cold Forged route and vice versa.


Many thanks

 

[Metalguy]

Chilled iron (white cast iron) was tried for tappets many years ago by Iskenderian (Isky), and possibly other cam grinders. They did not work well, but I don't know why.

Some of his ads stated that his lifters were not made of chilled iron.

 

[CoryPad]

The chilled cast iron process is supposed to result in a high hardness, high wear resistance part. The problem is that it requires cast iron, which has major problems with low mechanical properties (strength, toughness) and with high dimensional tolerances. The future for automotive tappets is high-hardness, low-friction coatings like Diamond Like Carbon, etc.

By the way, the cold forging process results in high mechanical properties (but not always wear resistance) and small dimension variation.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[venghatesan]

Hi Cory,

I found your information valuable. Thank you for the same. Can you please elaborate on "low-friction coatings like Diamond Like Carbon, etc."

Is it similar to "Molycote", used by Toyota and other Japanese OEs?

 

[CoryPad]

No, DLC's are not like Molykote. Look at this site for more information:

http://www.morganadvancedceramics.com/diamonex/

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.