Went through this many years back when a company I worked for tried to cost reduce a part by replacing a forging with a ductile iron casting.
This worked fine until our purchasing department decided to save a few extra bucks by going to another foundry. First operation was broaching a c. 2.5-inch diameter hole with a very large «keyway». Broach would typically last 7 to 10 8-hour shifts. When we started using ductile castings from the second foundry broach would not last even one shift.
First foundry used only slitter/stamping scrap for iron steel base. Second foundry used anything a magnet would pick up, including car bumpers [chrome and copper].
Standard analysis showed metal composition within spec (although first foundry was well within and second foundry was just barely within), and a Burnell hardness check indicated the castings were actually softer from the second supplier.
Even with a special anneal, the castings from the second supplier wore out the broaches in record time. Indeed, the special anneal seemed to make things worse.
We came across a magazine article that discussed the affects of using automotive scrap such as car bumpers [chrome over copper] on ductile iron castings. It turned out that copper causes chrome carbides to participate out in the grain boundaries. A bulk hardness test like the Burnell will not detect this. A micro-hardness test such as the Tukon (sp?) is required which is normally only done on case hardened items to detect the depth and degree of hardness. If I recall correctly, the special anneal caused even more of the chrome carbides to segregate/ precipitate in the grain boundaries.
The second foundry went bankrupt while we were working on the problem, tying up our casting tooling/patterns for nearly a year.
Overseas competition (mainly Korean) gained an OEM foothold while we were having materials problems. Domestic market penetration by offshore suppliers continued to increase, and after I left, the entire product line [representing over 100 jobs] was sold to another company and production was moved to India.
So much for value analysis and low dollar vendor selection. I was never able to find out why we did not re-source from the first vendor, but I guess the oats were cheaper after they have been through the horse.