失效及缺陷组织照片

风来疏竹

传统高速钢图片里的碳化物呈带状分布，不像前面那样成弥散分布，传统的材料性能没有前面的好，尤其是抗冲击性能没有前者好。我的初步分析，不知对与否？

hufadong

我认为不是蚀孔而是材料本身含有夹杂物，经过抛光出现的，我以前也见过有类似的！

leomet

40CrMo 感應淬裂, 肇因於初始組織不良.初始組織是假調質(軋延態, as-rolled)

[ 本帖最后由 leomet 于 2009-7-21 07:41 编辑 ]

leomet

原材料缺陷

undissolved interdendritic carbide film segments that formed

after ingot forging and left after austenizing, prior to quenching.

These carbides are very minute and are difficult to be detected with low price OM.
They are  toughness killers, therefore, Most of the toolings with
this kind of carbide film will fail prematurely, for sure.

Note: 固析者殺傷力較液析者大.

[ 本帖最后由 leomet 于 2009-8-12 23:45 编辑 ]

leomet

感應淬火時的熔融層淬油時增碳?

We see this once in a blue moon.

风来疏竹

189# leomet
专家能否谈谈浸蚀剂的应用情况？

leomet

190# 风来疏竹
FeCl, Nothing special.
試樣以高週波感應燒熔後入油槽. 無意中發現此層.

leomet

H13 原材料缺陷
A stressed part failed prematurely because of these cubic carbide particles.
Cracks were found to originate from sharp corners of  cubic "vanadium carbide(?)" particles.

Photo ~467, looks like sugar cube, does'nt it?

leomet

氫裂 caused by 過度酸洗

磷酸膜處理的齒輪未使用, 發現裂紋.

.........這些碳化物所處的晶界, 也是氫原子聚集的位置. 原子氫(H)一旦聚集成了分子氫(H2), 晶界上就有氣体壓力, 氣体壓力累積夠大時, 就會把晶界撐裂開來. 金屬科學上稱為”氫引發的破裂”(hydrogen-induced cracking). 高強度(淬回火)的鋼零件, 表面處理後都需實施去氫處理就是要避免此悲劇發生.

leomet

A hard lesson learned.
Faulty parts are being recalled in the  U.S.
A ball stud casing, supposed to have an induction-hardened case depth of 1 mm and 3~4 mm ductile core material to backup the brittle hardened layer.
This failed part was found to have a case that was induction-hardened all the way through, from inside out (>4 mm thick).  And the hardened-layer was not even tempered! Therefore the thru-hardened case is too brittle and was not able to withstand any slightest impact load.  Now, recall is the only way to reduce the future loss of money. There are over 12000 pieces out there in the USA market. Should a human life is lost, lawsuit will follow and money lost will be astronomical.

I was told that in the process of getting quotation for induction hardening a year ago, one very good induction heattreater quoted 0.8 RMB per piece. But  they turned to a cheaper offer of 0.5 RMB per piece from a heattreater which is less-experienced and has poor quality management. This tragedy doomed.

Penny wise and pound foolish is what I would describe this auto parts export company. This event will cost the owner of this company "an arm and a leg", but he will survive. I do hope that he would get back on his feet soon and do some overhaul to the management in his company.i

後記: 這老闆怕被國外求償, 趕快改了公司名.

leomet

194# leomet
A failed stress ring. Crack was found to originated from top of thread.
Very detrimental dendrite arm boundary carbide(arrowed) was found in its microstructure.

破裂面照明:  頂光 與 側光

leomet

195# leomet
JIS SCM 440, As-rolled. 假調質. Shown to you are very detrimental carbide "blades"
that will lead you to hell if you use this steel to make parts.
Color eteched to high-light carbide particles from matrix of ferrite.
Otherwise, finding  carbide in white ferrite would be like finding a white rabbit in a snow field.
white spots in photos 744, 746 are retained austenite?

leomet

Another 假調質. Most of the  carbide particles retained in white streaks after hot rolling.
Note:  Not all the white spots are carbide. Most of them are retained austenite, accompanied by carbide.
These white spots are named MA islands because they are highly alloyed.  M+A+K are what you find here..

leomet

Same steel as above.   Normal etching, without tinting.
本帖最后由 leomet 于 2009-10-30 09:23 编辑

leomet

枝晶間的空隙 interdendritic voids

txdd

铸铝109进行固溶与时效时的金相照片

固溶：


时效：


可观察到合金相的析出与形态变化

samling

非常好的资料
但是建议楼主每张照片标注放大比例

qquuaa

简直太精美了

yaozg

从未看见过如此多的、精美的金相图片，收藏学习了，谢谢

leomet

Faulty H13 in annealed condition. Its Q / T tooling for forging Al car wheel
failed prematurely because of its Giant grains.
Each view was taken as a pair---- of bright and dark fields.
Microstructure  THIS BAD does not come by often, you see this only once in a blue moon.