IGO 1

[smurali1]

Is there a standard which describes how Intergranula Oxidation has to be measured, how the sample has to be prepared, how the reporting (max. or average of x readings etc.,) has to be done.

 

[IRstuff]

Have you looked at the ASTM standards?

TTFN

FAQ731-376

 

[dbooker630]

I am not aware of a standard, and could not find any on a ASTM search using the keywords 'intergranular' and 'oxidation.'

Within my own shop I will look at a sample in the unetched condition at 500X magnification, and measure the deepest penetration observed.

 

[CoryPad]

I am not aware of any standards on this subject.

We inspect parts in the polished, unetched condition with an inverted metallograph, usually at 1000X. We measure the deepest penetration. Our limit is 15 micrometers maximum, which isn't very large at 500X.

 

[smurali1]

Dear all,

Thanks for the response.

We do measurement as per Dbooker630. i.e. 500x un etched condition.

However, the issue came up when HT shop did not concur with lab's finding. HT shop was not accepting that reporting of max. length is the right method. So, I wanted to check on standard's recommendation.

 

[IRstuff]

There is no ASTM spec for intergranular oxidation, but there are a variety of ASTM specs for measuring corrosion, including

http://www.astm.org/Standards/A763.htm,

which is referenced in one article discussing intergranular oxidation

TTFN

FAQ731-376

 

[TVP]

The following is an excerpt from ISO 6336-5, Table 5, Section 10.6:

Intergranular oxidation (IGO), applicable to unground surface. Determined by metallographic inspection of unetched coupon, if used. Limits in micrometers shall be
based on case depth as given.

The table then shows the requirements for class ML, MQ, & ME. The use of the word limits tell you that it is a maximum allowable dimension.

My company specifies that it is the average of the deepest
IGO over a minimum of 5 randomly selected areas.