Metals hardness

Jewelry Discussion
1

anyone know where to find the hardness (resistance to indentation)
of 18 karat yellow gold compared to brass, sterling silver and
bronze?

thanks
bill

2

Maybe somebody can point you in a direction, but the problem with
your question is simple. Which brass? Which 18kt? I know of 20
brasses just off the top of my head, and at least 1/2 dozen 18kt.
alloys, all of which have different hardnesses. In simple terms,
though, most 18kt. is softer than sterling, your typical bronze is
roughly the same as sterling, or a little harder (annealed), and just
about any brass will be as much as twice as hard as any of the others.

3 
    anyone know where to find the hardness (resistance to
indentation) of 18 karat yellow gold compared to brass, sterling
silver and bronze?

Which alloys? By that I mean that there are dozens of 18k alloys all
with different hardness and literally hundreds of brass and bronze
alloys. So you need to be specific as to which alloy you want
on. Information on most copper alloys (brass and
bronze) can be found on the Copper Development Association website at
http://properties.copper.org/servlet/
com.copper.servlet.CDAPropertiesSelectionServlet but you will still
need to know the alloy name and or number. For gold you are going to
have a hard time as most vendors have never tested their material
for hardness and so you will have to rely on very limited information
published in books like “Introduction to Precious Metals” by Mark
Grimwade. He lists a 18K yellow with 12.5%copper and 12.5% silver as
being 150 , 225 and 230 HV (Vickers) the variation is for annealed
, work hardened and aged(precipitation hardened) respectively. The
problem is determining what alloy you have as this is
only good for that particular alloy. Sterling silver ( the Silver,
92.5% copper 7.5% variety) he lists as 56 HV annealed, 140/180 HV
cold worked and 110/120HV aged.

Jim