Brittle Fracture of Metallic Diaphragm in Sonic Soot Blower

The diaphragm of sonic soot blower is commonly made of Ti-6Al-4V. It is significantly stronger than commercially pure titanium while having the same stiffness and thermal properties. This grade is an excellent combination of strength, corrosion resistance, weld and fabricability. Generally, Ti-6Al-4V is used in applications up to 400 degrees Celsius which is very good selection for used in boiler and catalyst for cleaning. Earlier in a research by the NRI, the diaphragms used to begin to crash quickly. Therefore in this current research, scanning electron microscope (SEM) has been utilized to discover the reason of failure of diaphragms that are used by the NRI. According to the SEM image of fracture surface of diaphragms, the crack generally divides into terrace-like steps when crossing a grain boundary is completely obvious. Moreover, the newly created different crack planes join together during further crack propagation producing a characteristic river-like pattern which clarifies mentioned brittle fracture. This can be guessed from the appearance review of the fracture surface since, in fracture surfaces there seem no symptoms of thinning and plastic deformation.