Fracture failure of connection pipe of truck diesel engine oil-collector

This paper describes the creep rupture behaviour, hardness distribution and microstructure of weldment made by submerge arc welding for W strengthened P92 steel. The cross-weld creep tests were carried out at 923 K and at stress ranging from 100 to 130 MPa. For stress below 120 MPa, weld-joints ruptured by the type IV crack, which located in their fine-grained heat-affected zone (FGHAZ) with the smallest measured cross-weld hardness. A strong drop in creep rupture strength of weldment was induced by brittle type IV failure. In addition to coarsening of M23C6 carbides and an equiaxed fine grains in FGHAZ, intermetallic Fe2(Mo,W) Laves phase precipitated on grain boundaries during creep is probably the significant factors caused the type IV failure.