leometwu的部落格

某國營事業單位10-4 送驗;       自稱金屬科老醫師(40年次)  所照的彩蝕金相照片,  不敢藏私, 與大家分享.

疲勞裂面=緩裂區 (abc線右側);  過載裂面=驟裂區;   此破裂屬: 單向拉應力, 單側, 多源點起裂. 

Photos of color etching that feast your eyes; Network of  carbide is very harmful to tensile strength and toughness of any steel. It is the culprit to this fatigue fracture.

Above: color etching 彩色腐蝕: T.M. matrix tinted and network of  carbide stands out; Below: normal nital etching: network of grain boundary carbide shown in color etching above, is nowhere to be seen here.

Dark field technique is used to high-light (凸顯)dispersed carbide particles and network of carbide.

Below: SEM photos;  GB Carbide (pointed by arrows) is well-known as "toughness killer"

Intergranular fracture, caused by G.B. carbides;  Fracture surface shows rock-candy(冰糖)feature.

此疲勞破裂的 root cause: 乃人員操作不當所引起. 板手長度是經過設計的, 不能隨興加長.