"Cheap' gun hammers and internal parts in general are usually case hardened low carbon steel. Usually a very thin case.

Check an edge on the part with a not-so-good file and see if you can file thru a thin case and into the soft core. If you can then there's your Case Hardening.

If the part had been made from through-hardening steel to begin with, the red heat and then cold quench needed for the C/Hardening would have 'through hardened' the part and you would have not found a Case.

If proper steel for and then through hardened and then possibly drawn back too far leaving it too soft for the job,,it would be just that,,too soft over all and no 'case' would be detectible on the surface,,thin or otherwise.

I usually just reshape the part if possible and then re-case with Case-n-ite.
Wonderful stuff, hard to get now. But the Cherry-Red case hardening powder works the same way. But I'm told by those who actually understand these things that Ch/Red hardens by using a Nitride (?) instead of a carbon infusion.
Makes the planet safer.

The CH on many of the inexpensive guns parts, and some of the not so inexpensive gun's parts, is very thin.
It's OK for sliding surfaces, but when battering takes place it simply crumples inward and is not of much help in keeping the surfaces shape.

A deeper case helps and you can get one with the above simple methods, but you need enough heat to do so.
Plain propane will do on small lightwt parts like a firing pin, screws, ejectors, sears ect.
A hammer starts to be too much for the small flame and you can't keep the part at red heat over all while the powder melts on the surface very well.

Oxy/Propane will do nicely for this.
O/A no problem but just be carefull you don't let the temp get too high and that bundle of melted powder with your part inside gets a little too brite in color/temp. It can melt away in an instance due to inattention.

The powders are also nice in that you can harden a specific area on a part (sear nose & pivot area for example) by just letting the powder adhere and melt onto that area.
The rest of the part (sear arm in this example) will remain in the soft state if that is what you desire.