Effects of Mo and S on Mechanical Properties of 15-5PH 1

[Maui]

Gentlemen, I am attempting to locate available literature that demonstrates the effects of Mo and S concentrations on the resulting yield strength and tensile strength properties of 15-5PH (XM-12). See the link below for a 15-5PH data sheet:

http://www.aksteel.com/pdf/markets_products/stainless/precipitation/15-5_PH_Data_Sheet.pdf

I am investigating how relatively small changes in weight percent for each of these trace elements (such that they do not exceed the maximum allowable chemical limits for this alloy) would impact these mechanical properties. Would you expect that increasing the Mo concentration by as little as 0.1 weight percent and decreasing the sulfur concentration to 0.005 weight percent would produce a measurable change in the tensile and/or yield strength of the material? Any knowledge that you could impart in this respect or literature that you could suggest would be of benefit.

Maui

 

[EdStainless]

I could see high S lowering the fatigue strength, but not the tensile properties.
I don't know why the Mo would have any impact.
I have no idea where to find data on this.

Look back at heats that you have used and see if the Mo varies enough to see if there is an effect.

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Plymouth Tube

 

[blacksmith37]

AS stated: S will have no affect on ten or yld, If very high it might make a marginal reduction in fatigue (as noted) or red. of area. Likewise the Mo would have no effect unless a few % were present - and that apparently would not meet spec.
Properties are going to depend totally on aging heat treatment. Never use a ppt hardening ss in the "S" (solution annealed) mill condition.

 

[metengr]

Maui;
Take a look at this AWS technical paper referenced below. There is mention of which elements effect precipitation strengthening, Mo is mentioned.

The precipitation-strengthened
martensitic stainless steels are used for
their high strength, higher than that of the
austenitic stainless steels, and good corrosion
resistance, better than the hardenable
400 series stainless steels (Ref. 1).
These alloys form a low-carbon martensite
with Mf temperatures just above
room temperature, and are precipitation
strengthened by one or more of the following
elements: Cu, Al, Ti, Nb and Mo
(Refs. 2–4).

http://files.aws.org/wj/supplement/aug99/BROOKS.pdf

 

[TVP]

Maui,

I looked through several reference books on physical metallurgy, etc., and could not find anything that would suggest a significant influence on tensile properties of either S or Mo in the amounts that you mentioned. Certainly there will be no effect of S on tensile strength within the range of 0.005-0.015, which is the range that I suspect you have. Mo substitutes for Al in the gamma prime precipitate, so it is possible that some Ni₃Mo could form, but I doubt that this occurs at such a low concentration of ~ 0.1%. Fe, even with an FCC lattice, has considerable capacity to retain Mo in solution, so there likely is not much driving force for precipitation until Mo is present in concentrations approaching 1%, not 0.1%.