Failure analysis of nickel 200 sintered filter cartridges

The premature failure of nickel 200 sintered filter cartridges used to separate the solid catalytic particles has been investigated. The failure is due to the formation of holes and transversal cracks, which occur preferentially on the upper part of the cartridges, near the welding. Microstructural and fractographic characterisation indicated that the failure started on the internal surface of the cartridges, which presented intense secondary intergranular cracking associated with corrosive attack. Fractographic examination on the surface of the transversal crack near the external surface indicated the action of a ductile intergranular fracture mechanism, while near the internal surface it featured a faceted and jagged topography, with cracks propagating inter and transgranularly. The results suggested that the premature of the cartridge failure was promoted by an environmental-assisted mechanism (stress corrosion or hydrogen embrittlement).