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Metal confusion


#1

Help!!! I am a G.G., former G.I.A. instructor, presently in-house
educator at Fortunoff. My specialty is gems and diamonds, but I have
recently been asked to teach a class concerning the precious metals.
As I search the web for info, I find lots of conflicting
Is this correct: “platinum is tougher (resistance to breaking) than
gold”? “gold is harder (resistance to scratching) than platinum”? Is
there a scale called vicks or vickers that lists metal’s hardness,
and if so how can I view this list. How does titanium compare to gold
and platinum in terms of hardness and toughness? Thanks,
Hillary Spector


#2

Hillary

There is a scale called vickers. What precisely it measures though I
am not sure. If you have a 1998/99 Hoover and Strong catalog on page
10 it lists the vickers scale numbers for many metals and alloys
(though not titanium) in its soft tempered state. There it also
states that “vickers scale is used to test the tempers of precious
metals. We have provided these numbers for you to compare against
metals that you may be familiar with. Our sheet and wire tempers
will run 50 - 100 points higher than soft temper matierials”.

For example it gives a vickers soft temper number of pure platinum at
52V and pure gold at 30 V. The 18 K gold alloys range from 265V for
nickel white gold to 104V for yellow. Platinum alloys range from
117V for 90% pt/ir to 130V for plat/s+.

Platinum is, in your words, “tougher (resistant to breaking) than
gold” in that platinum alloys are of a higher karat (90 %) than
commercially used gold alloys (41.6 to 75%). Pure platinum vs pure
gold is a tough one. They are both very resistant to breaking as
they do not age or work harden. As far as scratching goes, again it
depends on what alloy you are talking about. Pure metals are equally
awful in the scratch test catagory. I would suggest talking to a
metalurgist. Call the people at Hoover and talk to thier
metalurgist, I can’t remember his name but he recently won an award
for a paper he wrote on metals. He would be a wealth of knowledge.

Larry Seiger


#3

Dear Hillary,

    Is there a scale called vicks or vickers that lists metal's
hardness, and if so how can I view this list. How does titanium
compare to gold and platinum in terms of hardness and toughness? 

The definition of vickers hardness is written on
http://www.britannica.com/eb/article?eu=212&tocid=0

The list I have is below, and could not find that of titanium.

arroy   annealed        hardened

K24     25-35            80
K24(*1) 50              120
K24(*2) 35-45           80-95
K18     70-180(*3)      150-280(*3)
Pt1000  50-55           100-110
Pt900   70-75           120-130
Pt850   120-130         260-280
Pt1000(*2) 80-90        160-180

*1: with minor constituent
*2: with minor constituent for casting
*3: depends on the arroys

I don’t know about measures of toughness for metals.

Hope this helps,
Takashi Tomoeda
@Takashi_Tomoeda1