4140 prioir austenite grain boundries dangerous in drilling equipment
4140 prioir austenite grain boundries dangerous in drilling equipment
(OP)
HI all
I have some questions regarding the micro structure of 4140 steel. It is widely used in the drilling equipment. Is it possible that prioir austenite grain boundaries can be present in quenched tempered conditions or is it possible to reveal the prior austenite grain boundries using 2% Nital?
1 more question presence of prior austenite grain boundaries are desirable or are dangerous to the integrity of the material.
Thanks
I have some questions regarding the micro structure of 4140 steel. It is widely used in the drilling equipment. Is it possible that prioir austenite grain boundaries can be present in quenched tempered conditions or is it possible to reveal the prior austenite grain boundries using 2% Nital?
1 more question presence of prior austenite grain boundaries are desirable or are dangerous to the integrity of the material.
Thanks





RE: 4140 prioir austenite grain boundries dangerous in drilling equipment
http://vacaero.com/information-resources/metallogr...
RE: 4140 prioir austenite grain boundries dangerous in drilling equipment
What is more of a concern is that the structure be fully tempered martensite. That is the desired structure.
The worry should be about retained austenite and similar issues.
In alloys with suitable grain refiners the final structure will always be fine grained, there is no reason to check.
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P.E. Metallurgy, Plymouth Tube
RE: 4140 prioir austenite grain boundries dangerous in drilling equipment
RE: 4140 prioir austenite grain boundries dangerous in drilling equipment
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: 4140 prioir austenite grain boundries dangerous in drilling equipment
That is why i am confused because with nital you cannot see prior austenite grain boundries.
RE: 4140 prioir austenite grain boundries dangerous in drilling equipment
You can see prior austenite boundaries with nital in some cases, depending heavily on thermal history. In the as-cast coarse prior austenite state the boundaries are very clear with nital.
RE: 4140 prioir austenite grain boundries dangerous in drilling equipment
RE: 4140 prioir austenite grain boundries dangerous in drilling equipment
RE: 4140 prioir austenite grain boundries dangerous in drilling equipment
Dirty steel, improper heat treatment, insufficient hot/cold reduction, and a few other things.
We Q&T 4140 to P110 properties regularly. All that you see is tempered martensite. If you see anything else you have problems.
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P.E. Metallurgy, Plymouth Tube
RE: 4140 prioir austenite grain boundries dangerous in drilling equipment
Most rotary shouldered connections need 120KSI yield and 40 Ft-Lbs Charpy Impact. If the material does not meet these properties, that is at least part of the problem.
In the section thicknesses used in mud motor top subs, it is unlikely that you will obtain these properties with 4140. Yes, it can be done, but most quality manufacturers will use a modified 4145 (with increased Cr & Mo for improved hardenability) to be absolutely sure there will not be a material problem. If the top sub was manufactured at a small shop using "commercially heat treated" 4140 bar stock, then downhole failure would be expected. There is a reason the quality manufacturers charge more for their tools.