[Geof]

Your question is not really answerable because any answer involves so many assumptions.

You can calculate the kinetic energy that the swinging ball has at the bottom of the swing; it is the same as the gravitational potential energy at the top of the swing, mass * g * height. I am ignoring friction because it is very low in the setup you are contemplating.

The kinetic energy of the falling ball is transferred to the next ball on impact and the way energy is transferred in this situtation is mostly by elastic deformation of the steel ball while the moving ball exerts a force on the next ball. This is where it gets awkward to calculate meaningful numbers. When two spheres make contact the area of contact is very, very small; indeed if the spheres are perfect and do not distort the area is infinitesimal and the pressure is very high. But the spheres do distort so the area of contact increases and the pressure of course declines.

Really the only answer that can be correct in any way is that the pressure is not enough to cause plastic deformation on either steel ball.