Where the
world gathers for metal finishing
Q&As since 1989


-----

Cracks after hard chrome plating on ground induction hardened piston rods

We have observed cracks developing after chrome plating on ground induction hardened medium carbon steel piston rods. The development of cracks have been found to be located on the induction hardened portion only and does not extend to un-hardened part. The cracks appear like a net like the grains size as seen in a micro-structure.
looking for possible reasons.

Saibal Bhowmick
vendor for ground steel bar - Faridabad, Haryana, India
February 19, 2009

Hard chrome has always a very high internal stress in tension. The outer layer of your substrate is also under tension. Both stresses add up and the elastic limit is surpassed, so, cracks occur. You need to induce some compression in your pistons before plating and tailor the temperature gradients of your plating cycle.

Guillermo Marrufo
Monterrey, NL, Mexico
February 23, 2009