失效及缺陷组织照片

leomet

A failed hydralic valve.

A combination of overload + E-type graphite distribution
might be the cause of  this failure.

leomet

Intergranular carbide

A ticket to hell for hardened irons and steels.

鑄鉄與一些中高碳(合金)鋼, 由於凝固偏析, 鑄態下 最後凝固的位置 因為溶質(solute)原子濃度特高 常會有碳化物薄膜出現,
此物有時遺留到鍛後 使鋼材(例如H13)延伸率(韌性)大幅度劣化.
Elongation/toughness of cast irons,  or alloyed steels with medium to high C%,  will be greatly reduced if such carbides
are present in their microstructures. Remains of it after hardening are very minute. Most of the time,  it is difficult to see them
clearly under LM, but their bad effects exist. Quench cracking is prone to happen if  this carbide films exist in the microstructure.
------And more often than not, heat treaters become the scapegoats.

leomet

Can you correlate the following photos to #204?
Arrowed segments of white lines are "retained carbides"
after austenization. Before austenization, they were longer,
and thicker in size. During austenization, part of them went
into solid solution.

catcmt

与Leomet 老师探讨5楼的照片，
请问是否观察过未腐蚀的这些高碳马氏体的照片？未腐蚀前有裂纹吗？
就本人的观察，裂纹是在腐蚀后产生的。而不是相变时产生的。

leomet

回复 206# catcmt
No comments.

catcmt

我做过一些实验，发现抛光后观察，没有微裂纹。腐蚀后在马氏体片上才观察到有微裂纹产生，并且在最初的时间里，随时间的变化，裂纹逐渐增多。

leomet

JIS SKD61, AISI H13. As-cast.
Note the intergranular carbide particles(液析) and films(固析).

mengyiyang

真实好东西  呵呵    好好学习下

wuwenlier

回复 19# leomet


    太有参考价值了

紫丁香

学习了。这么精彩的图片，开眼了。

jeffers

大师就是大师

永无止境she

请教leomet 老师，首先赞一个，很精致的金相图片，这需要很高超的制作技术！很佩服！  老师您能为10楼的问题解答一下原因吗? 等待你的回复。谢谢！

confirmvvv

非常全面，非常感谢

frank007

吴老师知识渊博啊，值得学习！

leomet

H13 tooling (for Al. car wheel forging) that died very young because of this bad microstructure.
Photos 786, 792 show much smaller prior Austenite grains formed during hardening of tooling.
In these 2 photos, old GBK is not clearly seen. Note the retained carbide film along the old grain boundaries.
They are very detrimental to toughness of toolings.
This G.B. Karbid are commonly found in large-size round stock of tool steels.
They appear, in the steel mill,  during ingot forging and the following
quenching process for spheroidization of carbide particles.
Most tool steel supplies will cheat you, saying  that it was caused in your hardening process.
Next time, when they say this again. Tell him he is a  liar.
.
.

yanhaisheng007

啥也不说了，吴老师的专业水平是一般人够不到的高！
以吴老师做榜样，好好学习

leomet

回复 202# leomet


    Marcro photos to #202:

The 3rd photo is a micro photo, 50x  at 10x8cm.
Material: H13.   Repeated re-heating  (10 time?)  back to the
forging temp of ~1200C in the process of ring forging. That's
why they got the "giant grains".

leomet

Quality photos from one of the best, and probably
the oldest (60) hands-on metallurgists in Taiwan

Prior Austenite grainboundaries, old and new.
Can you tell them apart?

Old: existed prior to austenization.
New: produced after austenization, before quenching of the tooling.

leomet

This set of photos are from the same tooling as the previous post ---(#220).
Shown to you are retained carbide "blades" (arrowed) after Q/T, which are detrimental
to toughness of any steel.

17qqwzh

回复 181# 97bigboy


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