Cr27Ni7链节钢断裂失效的显微组织分析

Failure Analysis on the Microstructure of Cr27Ni7 Chain Link Steel

借助光学显微镜、扫描电境、显微硬度计和X射线衍射仪等手段,对不同服役周期的链节进行了显微组织分析,确定了Cr27Ni7链节钢断裂失效的显微组织原因。结果显示,链节在900℃高温热循环条件下长期使用,其显微组织中的碳化物类型发生转变以及晶界弱化,显著地降低了Cr27Ni7链节钢的冲击韧性和拉伸塑性,即使没有冶金缺陷(缩松、夹杂物),也已使链节接近或达到其使用寿命。为延长使用寿命,可采用高温晶界强化和添加取代铬的使碳化物更加稳定的少量合金元素。

The fracture failure on the microstructure of chain links with different term service has been analyzed by means of optical microscopy, scanning electron microscopy, microhardness tester, and X-ray diffractometer. The results show that the changes of carbides in the microstructure and grain- boundary weakness decrease tensile strength and impact toughness obviously, even though, without metallurgical defects （shrinkage porosity, inclusions）, under long-term service of 900 ℃ thermal cycling conditions, which cause Cr27Ni7 chain link steel to approach or reach its lifespan. In order to prolong the service life of Cr27Ni7 chain links, trace elements instead of chromium should be added to strengthen grain boundary and form more stable carbides.