Effect of Carbon on Hardness in Martensite

[Jerrod Miller 561]

Ran across this interesting table and graph, thought I would share.  The source cited (4) is Siebert, Doane & Breen, The Hardenability of Steels, ASM, 1977.  

Moral to the story:  Not only does an increase in carbon increase the ability of martensite to form, but it also corresponds to an increase in hardness for the martensite as well.  I don't have the source material at hand, but I think it is safe to assume that "excessive" alloying elements besides Fe and C will also change the overall hardness.  The paper I was reading that this chart appeared in did not go into any specifics in this case either.  

[Joël Mercier 623]

I did also read that the maximum amount of carbon that will increase hardness in simple carbon steel is around 0.9%. Is that right? This would explain why Aldo chose to use 0.91%C in his W2.

[Gary Mulkey 1,444]

Interesting.  It appears that 99.9% martensite can be achieved with .5%C.  I was under the impression that it would  take .7%.

[Alex Middleton 788]

Out of curiosity, what % of martensite can the average backyard smith expect to yield using simple steels and quenching at decalescense?

Edited April 17, 2019 by Alex Middleton

[Jeremy Blohm 561]

Thank you Jerrod for sharing. 

[Jerrod Miller 561]

2 hours ago, Gary Mulkey said:

It appears that 99.9% martensite can be achieved with .5%C.  I was under the impression that it would  take .7%.

I can't say for sure, but my understanding would be that they are doing a microscopic (likely Vicker's) hardness on a localized patch of martensite, avoiding the ferrite/pearlite around it.  The sample as produced would not be 100% martensite.  

[Jerrod Miller 561]

28 minutes ago, Alex Middleton said:

Out of curiosity, what % of martensite can the average backyard smith expect to yield using simple steels and quenching at decalescense?

Assuming something like 1084, pretty much 100%.  

[Alex Middleton 788]

Thanks Jerrod, that's good to know.