Dear Master! what are the lines inside the grain about the picture x2.jpg ? Are they the sub-bound ...
It is my opinion that those fine lines you referred to are not sub-boundaries. They are crazes on a deposited film.
In color etching, colors are produced by reflection from thin films deposited on the matrix. If the films get too thick, crazes like these will show up after drying by hair dryer. 谢谢老前辈指导，这个图片更能形象地证明我的论点。 leomet 发表于 2008-3-7 21:21
P/M 高速钢 金相
P/M = PowderMetallurgy
马氏体加颗粒状碳化物加残余奥氏体，仅个人意见 leomet 发表于 2008-3-4 07:59 static/image/common/back.gif
加工後才发现小孔 ~ 1mm, 请高手参与讨论. 是蚀孔? 还是小气孔被挖开口?(opening up oftrapped gas holes ...
我感觉您判断为蚀孔是对的，不锈钢点蚀形貌和P1011396照片很接近，且孔底部隐现晶界。感谢您上传了这么多珍贵的资料，向您学习！班门弄斧了，见谅。 本帖最后由 leomet 于 2014-2-24 06:06 编辑
這位半瓶水(40+)老外金相工程師, 寄來這些照片說是裂紋, 要退我們的貨!.
晶界碳化物
本帖最后由 leomet 于 2013-5-15 22:14 编辑GCr15 ~ JIS SUJ2 poor microstructure
http://www.rclbbs.com/forum.php?mod=viewthread&tid=154558&page=1&extra=#pid1236618
就是這軸承 本帖最后由 leomet 于 2013-5-18 06:17 编辑
SCM440, induction hardened. Corner locally over-heated,coarse grains obtained and workpiece cracked on quenching.These beautiful photos of Martensite are obtained by color etching, with a bit of luck. If you look closely, you will find grain diameteris the largest at the bottom of the photo because it is the edge of a hole where induction heat concentrates. Crack is not shown here but it initiated from the corner ofa hole. At the bottom, grain diameter is about50~70 um which is too coarse and workpiece cracks readily on quenching. Perfect photos! Great people! 本帖最后由 leomet 于 2013-8-7 00:37 编辑
穩定桿 疲勞斷裂. 送來分析.
珠擊/拋丸過度 產生的微裂, 成了起裂點.
leomet 发表于 2008-3-3 12:57 static/image/common/back.gif
金相欣赏 S45C 淬裂
JIS S45C0.45%C
吴老师，如何确定它是过热引起的淬火开裂？ leomet 发表于 2008-3-11 19:04 static/image/common/back.gif
8620 滲碳. 後天才有時間切片, 檢查其金相. 有失效分析的同行願先表達看法嗎?
3/13 : 試片沒做好, 表面失 ...
版主，你好，我以前在一家日资企业做过类似的工件，材质要求是SCM415或者SCM420，在国内一般都是用20CrMo，工艺：渗碳淬火回火，从你的失效件来看，第一：18MM的外径，0.3的有效硬化层深度过于浅，强度不够。第二：从你所提供的显微硬度值来看，渗层和心部几乎没有一个过渡区（共析区），硬度骤变，此类情况极易造成工件断裂，第三：心部硬度有些偏低，韧性和强度会偏低，以上都是本人愚见，请版主指点一二，向台湾同胞学习 谢谢楼主，很好的经验分享 本帖最后由 leomet 于 2014-1-5 16:51 编辑
P/M 高速鋼過熱金相照片
http://leometwu.pixnet.net/blog/post/34485907
請讓我知道, 你是否可連結上這個台灣網站. Thanks for providing failure analysis of stabilizer bar.I fully agree with your point. qlf_126 发表于 2014-1-5 08:30 static/image/common/back.gif
Thanks for providing failure analysis of stabilizer bar.I fully agree with your point.
That is the only cause of the failure.
Stablizing Rod over-peening damage
本帖最后由 leomet 于 2014-2-7 22:34 编辑More photos for #332; The first photo: fracture surface cut by EDM wire-cutting.
photo 1, 1b show microcracks created by overpeening.
Note on photo 1b: highly strained layer etches white.
本帖最后由 leomet 于 2014-2-24 06:08 编辑
熱鍛模破裂...
紙張上設"車縫線" 可使其易於撕裂. 晶界上的碳化物對於鋼鐵基地, 就如紙張上的"車縫線".
延時破裂, 應力釋放破裂, 靜置破裂
本帖最后由 leomet 于 2014-2-25 16:55 编辑delayed cracking 照片順序 由下往上.
放著就破裂的螺絲
殘留應力引起的破裂, 稱: 延時破裂, 應力釋放破裂 (delayed cracking;stress relaxation cracking)
工序: SCM415 1. 表面滲碳淬火 → 2.回火至約 30HRC 3.一端高週波硬化(HRC65)→ 4.噴砂 5. 端面拋光
→ 成品 → 6. 120℃回火
客戶來郵更正
工序: SCM415 1. 表面滲碳淬火 → 2.回火至約 30HRC 3.一端高週波硬化(HRC65)→ 4. 160℃回火 5.噴砂 6 端面拋光 → 成品
這回火溫度太低了! 無法消除淬火應力. 所以............
They say " A single picture worthes a thousand words".
接上面 delayed cracking
本帖最后由 leomet 于 2014-2-24 07:10 编辑leomet 发表于 2014-2-24 06:17 static/image/common/back.gif
delayed cracking
銹蝕過程產生蝕孔與氫原子, 蝕孔加大應力集中效應, 氫躜入基地, 兩者都增加破裂機率. leomet 发表于 2009-10-10 09:10 static/image/common/back.gif
氫裂 caused by 過度酸洗
磷酸膜處理的齒輪未使用, 發現裂紋.
请问前辈，如果弹簧出现氢脆裂纹，会同时出现几圈螺旋状裂纹吗？