The influences of different filler metals on the microstructure of Invar Fe-36Ni alloy multi-layer multi-pass MIG welding

Abstract

The Invar Fe-36Ni alloy plates are welded by multi-layer multi-pass MIG welding with two kinds of filler metals in this paper. The microstructure of the joints is studied using scanning electron microscopy, x ray diffraction, and energy dispersive x-ray spectroscopy. And the morphology and microstructure of the joints with two different filler metals are compared. Moreover, the element distributions at different location are discussed. The results indicate that there are no pores or crack defects on the surface of the weld seam. The sizes of the incomplete fusion, which occurred in the interior of weld seam, using stainless steel filler metal are much larger than that of using Invar M93 filler metal. The distributions of elements in the interlayer are homogeneous using two filler metals. However, the element distributions, which are perpendicular to the fusion line, are not uniform using steel filler metal. The experimental results illustrate that the M93 Invar welding filler is better than stainless steel filler metal for multi-pass welding process of Invar Fe-36Ni alloy.