to find the type of crack based on surface appearance. 1

[Adnan Nadaf]

hello everyone,
i need to find that what type of crack is it? Is it possible to differentiate between cracks visually whether it is quench crack or RM crack or Grinding crack? and what is the corrective action to avoid such type of cracks.the material is En353 and case carburised and then finish grinding is done.
2. i have a similar type of issue in forging of Forks of tractors, i am constantly facing crack issue in forging. please suggest me some corrective actions to avoid crack in SAE1045 forging.

 

[swall]

It is not clear if the material in this case is a forging, but the discontinuity you show appears to be some interdendritic separation from over heating (burning).

 

[Maui]

You need to have a metallurgical analysis performed in order to identify the nature of the cracking. This is a destructive test. You can sometimes differentiate cracks from their appearance and a knowledge of what processes the material was subjected to at the point where the crack was visually identified. For example, if the crack was observed after cooling down from forging but before heat treatment, then you know it wasn't a quench crack.

Maui

 

[metengr]

Agree with the metallurgical analysis. The example above could be grain boundary oxidation that can happen with case carburized components.

https://vacaero.com/information-res...r-oxidation-igo-intergranular-attack-iga.html

 

[EdStainless]

Sometimes you can polish the surface and then etch it to see the crack pattern.
But in most cases you need to remove a portion and section it to really know.

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P.E. Metallurgy, Plymouth Tube

 

[mfgenggear]

Typically I have seen such issues when procedures are not being followed in heat treating. Basically the forging specification, and the heat treating specification. For example not proper preheat. Prior to hardening. Or not tempering with in the required time. Look at the procedures of those manufacture the parts. And also agree a failure analysis is required.

 

[RolMec]

A reference worth checking might be this:

http://www.researchinventy.com/papers/v2i11/A02110105.pdf

Similar effects as per the pictures come from nonmetallic inclusions which are formed out into linelike surface flaws during rolling / forging and result in surface cracks during heat treatment.

Roland Heilmann
Lpz FRG

 

[Adnan Nadaf]

Thanks for your valuable replies,i will get back to you with inspection details.