Regardless of how it is done, a hard surface over a softer substrate is called
a case. The OEM lifters that I have used rarely had a case more than 0.020"
thick, and in practice, damage to the bottom surface of a lifter normally
means that either the hard layer is worn through or otherwise damaged and
thus unsuitable for further use. I have been experiencing problems with OEM
lifters since the early 80s (after the B20 went out of production) and thus
will not use them if any other alternative is available. There may have been
some good years but probably NOT the later years, when B20 and B30 engines were
so notorious for cam and lifter problems that the petroleum industry developed
the "Volvo B20 cam and tappet test" for engine oils. (Unfortunately my efforts
to obtain more info on this test have thus far been unsuccessful but you can
find references to it in some of Phillips Petroleum Company's [Now Conoco Phillips]web pages.)
By the way I think my credentials for this judgement are adequate. I am a professional metallurgist with over 40 years experience in mechanical failure
analysis, aircraft overhaul metallurgy, welding, and tropic deterioration of materials. I graduated from Stanford University.
Now that I am retired my professional registrations have lapsed but I was formerly registered as a Professional Engineer in Oklahoma, Texas and the Canal Zone.
--
George Downs, Bartlesville, Oklahoma, Central US