Thanks Mr the Dude,

This is existing piping, and unfortunately the layout change is not option. The high stress is due to seismic induced X-mas tree rotation. All other stresses (sustained,expansion, seismic and slug) are well within the code allowable. The material upgrade is one of the options I would like to present to clinet with a number of other possible solution. All I want to know is the weldibility between two specific materials. Yes we have material specialist in our company to consult about this issue.