50 HRC..... 465 custom vs 440c 10

[fapper]

There are two kinds of heat hardenable steels,those that have carbon so carbides are created,like 440c and then the PH martensite steels like 17-4 or custom 465.

The carbide steels like 440c can have higher peak hardness than hardest PH steels like custom 465,but what if I heat threated and aged both steels to be 50 HRC?

They way I see it is this,at 50 HRC the 465 us significantly more corrosion resistant and tougher than 440c,the yield strenght is about the same,why would I then choose 440c or other similiar carbide steel at 50 HRC over custom 465?

Is the HRC rating missleading? Will the carbide steel at same HRC rating have improved scratch,abrasion or wear resistance?


Another comparison would be 10-2-3 Beta titanium hardened to 48 HRC vs some Stellite alloy with similiar HRC rating.The titanium is worst when it comes to galling,and Stellite is best,but for abrassion and scratch,would there be difference if they have same HRC becose Stellite got carbides and beta titanium doesnt?

 

[EdStainless]

Totally different mechanisms at action. So different structural factors come into play.
If you need to make a cutting device (shear or razor blade) that has corrosion resistance use 440C.
If you need strength with usable impact and fatigue properties then use C465.
Abrasion resistance is a complex function of the martial causing wear, its velocity and angle of impact.
Ti will never stand up well in wear situations.
Co alloys (even those with no carbides) have incredible resistance to galling and cavitation, and most forms of surface contact wear.

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P.E. Metallurgy, Plymouth Tube

 

[fapper]

but why?

Why would one 50 HRC steel cut hair and resist abrasion any different than another steel that have 50 HRC but also have carbides?

I was thinking if the materials have same HRC,their abrasion resistance must be completly identical.Do carbide steels offer better abrasion resistance even if they are same rockwell C hardness than precipitation hardened steels without carbides?

 

[metengr]

Sometimes people place to much emphasis on hardness for comparison purposes. Hardness is only a measure of resistance to local indentation and only one of several parameters with which to judge wear properties of materials.

 

[fapper]

what other parameters do you mean?

 

[metengr]

Yield strength, shear strength, notch toughness, fatigue....to name a few and dependent on the type of wear in service.

 

[fapper]

I am only interested in abrasion resistance

back to the topic,if I have two steel plates,both measing same HRC value but one contain carbides,will they have different scratch and abrasion resistance? Like the examples above,stellite vs 10-2-3 titanium at 48 hrc.... or custom 465 vs 440c at 50 hrc,do carbide containing alloys have higher scratch resistance than non-carbide alloys even through they can measure same rockwell c value?

 

[metengr]

if I have two steel plates,both measing same HRC value but one contain carbides,will they have different scratch and abrasion resistance?

Yes.

You can do your own information search.

 

[arunmrao]

Abrasion resistance is also affected by the type of carbides, if they are M3C or M7C3 or M23C6 types. Also their size and distribution matters. Finally, the matrix holding these carbides is important, in a soft annealed condition, the carbides will be easily gouged or dislodged, thus affecting abrasion resistance.

Thus, hardness cannot be considered to be a true measure of wear resistance.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[EdStainless]

fapper, there are books on this subject.
Wet or dry, what size is the abrasive, how hard is the abrasive, how fast is it moving, what is the angle of impingement
All of these matter a lot.
Superficial hardness can only be used when comparing similar material for wear resistance.
When you change alloy type it is meaningless.

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P.E. Metallurgy, Plymouth Tube

 

[fapper]

but generaly,do carbide containing steels outperform non-carbide steels in abrasion resistance if they are both at same HRC hardness?

If I get 50HRC from carbides,is it superior type of hardness than if I get 50 HRC from martenistic heat threatment or cold working? Is there anything special about carbide containing steels or alloys that isnt revelead by HRC test? If I need part to be scratch resistant,why would I go with carbide steel if I can cold work or age another steel without carbides to the same 50 hrc,wouldnt it be roughly equaly scratch resistant?

The type of abrasion I mean is when you for example take piece of metal,like screw and drag it with certain pressure across polished plate.If one plate is 440C and other custom 465,and they are both aged and heat threated so they both measure 50 HRC,would there be any noticable difference in how they are scratched just becose 440C is 50hrc with carbides and 465 is 50 hrc without carbides?

 

[EdStainless]

How hard is the screw, what is the pressure, is there any lubricant, what is the speed?
And scratch resistance bears little relationship to general abrasion resistance.
I know of now such general relationship based on hardening mechanism.

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P.E. Metallurgy, Plymouth Tube

 

[Maui]

The wear resistance of a material depends not only on the condition and type of material itself but also on the environment and manner in which it is being used. This is one of the main reasons why wear resistance properties are at best poorly defined in the literature. How these alloys are actually being used matters. The answer to the question you posed

but generaly,do carbide containing steels outperform non-carbide steels in abrasion resistance if they are both at same HRC hardness?

is generally yes when these different alloys are being used in the same application under the same conditions. It is easiest to explain this using high speed steels as the example, since these types of steel alloys are often used in applications where their excellent abrasion resistance and high attainable hardness are requirements.

The wear resistance of high-speed steels is strongly dependent on the amount, type, size, shape, and distribution of the alloy carbides that are present in the microstructure. The function that these carbides serve can be understood through the use of an analogy. Consider the appearance and function of a cobblestone road: The alloy carbides that appear in the tool steel microstructure serve a purpose that is comparable to the function of the wear-resistant cobblestones in the road — they provide a very hard contact surface area that is extremely resistant to abrasion and wear. And the mortar that holds the cobblestones together is much like the steel matrix that holds the carbides together in the alloy. Many different types of carbides can be formed, depending on the chemical composition of the alloy. Carbide types are normally identified in a basic sense by their chemical composition. For example, in the microstructure of vanadium carbide, there is a one-to-one ratio of vanadium atoms to carbon atoms, to form the carbide phase VC. This one-to-one ratio is usually expressed in a generalized way by the expression MC, where M represents the alloying element of interest (in this example, vanadium) and C represents carbon. Many other combinations are also possible. Cementite, the carbide typically found in plain carbon and low-alloy carbon steels, is an M3C-type carbide consisting of three atoms of iron and one atom of carbon to form Fe3C (the text editor will not permit me to make the 3 a subscript to Fe, but that is what it is supposed to be). Steels that contain appreciable amounts of manganese also form an M3C type of carbide, namely Mn3C. Manganese and iron have very similar atomic weights, and both of these carbides are typically found in combination. But more complex carbides are also represented using this terminology. The M3C carbide can be thought of as having a chemical formula of (Fe+X)3C, where X refers to different combinations of manganese as well as the four major alloying elements, Cr, V, W, and Mo. The precipitated metal carbides such as MC and M2C can attain very high hardness, and they contribute significantly to the wear resistance of high speed steels that are alloyed to contain large volume fractions of these particular carbides. Depending on the alloy composition, many of these steels usually contain more than one type of carbide. For example, in annealed M4 high-speed steel the carbides are a mixture of types MC, M23C6 and M6C. In practically any given high speed steel, the wear resistance depends on the hardness of the steel. Higher hardness, however achieved, is an aim when highly abrasive cutting conditions will be encountered. For the ultimate in wear resistance, carbon content can be increased simultaneously with vanadium content to form a greater volume percent of extremely hard vanadium carbides. Steels T15, M3 (class 2), M4, and M48 belong in this category, and all exhibit extremely high wear resistance.

Maui

 

[mfgenggear]

great info every one save as notes.

 

[arunmrao]

Maui, your analogy of cobble stones is a good one. I would use a plain vanilla ice-cream that tastes bland, but improves with addition of toppings.
A great explanation Maui.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[Maui]

Thanks Arunmrao.

 

[EdStainless]

The cobblestone analogy is good, now instead of wheels imagine that the wear is from sharp steel needles.
In this case the wear can attack the mortar and undercut the binding holing the stones in place.
This is why size, hardness, and angle of attack are so important.

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P.E. Metallurgy, Plymouth Tube

 

[fapper]

thank you Maui,that was very good post about carbides

you say it is generaly true that carbide containing steels/alloys outperform other non-carbide steels/alloys at same HRC,you didnt explain why.You explained very good the carbide stuff,but not why,at same hrc,why would carbide containing steel outperform non-carbide steel.

You say the carbides are like hard cobbles and the steel matrix is like the mortat.I wonder,why even bother with carbides/cobbles,why not just use super hard mortar/steel matrix?

10-2-3 titanium can go up to 48 hrc
custom 465 goes to 50 hrc
tribaloy T-800 = 62 hrc

none of these have any carbides.I know the tool steels have higher HRC like 65 and in that range non-carbide steel is not an option,but in the lower hardness range,what is so special about carbides that I would take them over non-carbide alloy/steel if they measure exactly same in HRC test apart from other parameters that doesnt have anything to do with hardness like galling and corrosion resistance.

 

[MagBen]

With a same MACRO hardness, A steel with carbide structure is supposed to have a much better wear resistance than that without carbides. The reason is simple, refer to Maui's Cobblestone Analogy, the cobblestone/carbide has a very much higher hardness than the soft matrix, which can protect the whole material from wearing. Assuming the abrading medium has a hardness of 60HRC, Customer 465 or a tool steel (with 50HC)will be worn down quickly, while the steel with carbides will probably not because carbides are much harder than 60HRC.

It is safe to say a higher hardness generally leads to a better wear resistance, when the materials belong to one family with similar microstructures.

 

[tbuelna]

Here is a paper about rolling element bearing steels that might be of interest. The part about the influence of carbides starts on page 16.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120008557.pdf