The hat ductility behaviour of a material exhibits a good correlation with
its heat affected zone (HAZ) hot cracking sensitivity. This study was aimed
at evaluating the HAZ hot cracking susceptibility of 18% Ni maraging steel
and exploring the relationship between hot ductility and microstructure of
the HAZ in an 18% Ni maraging steel. optical metallography and scanning el
ectron microscopy (SEM) investigations revealed that the ductility loss was
accompanied by fracture transition from ductile transgranular mode to brit
tle intergranular made. Fracture specimens were examined using SEM with an
attached energy dispersive X-ray spectrometer. The SEM fractographs indicat
e that the ductile transgranular dimple fracture (i.e. coarse) surface was
the titanium rich inclusion precipitated at the grain boundary, which promo
tes microvoid nucleation, growth, and coalescence and leads to localisation
deformation until final fracture. Results of hot ductility tests also indi
cate that the titanium I ich inclusion can reduce the ultimate tensile stre
ngth without reducing the tensile ductility. The appearance of brittle inte
rgranular fracture is caused by the constitutional liquation of titanium su
lphide inclusions that induces formation of a liquid film penetrating the g
rain boundaries. The results show that titanium sulphide inclusion nor only
reduces the HAZ tensile ductility, but also reduces the ultimate tensile s
trength.