Technology maturity index
Traditional welding experience leads to mature technology
Industrialization maturity index
Digital process chain challenging for industrialization
Design and applications
Large size applications drive technology development
Materials and alloys
Standard welding experience enables large material portfolio
A wide range of materials and process settings are available for traditional electric and plasma arc welding technologies. In principle, these can be used in their Additive Manufacturing equivalent. Therefore, large variety of wire material exist and can be sourced cost efficient at multiple suppliers.
Good material properties as long as 3D toolpath and heat distribution are under control
Parts fabricated using Wire Arc Deposition usually show high density of more than 99,9 % and good mechanical properties. In the left micrograph a typical cross-section of a Powder Laser Deposition component is displayed with no larger pores or defects visible. However, insufficient heat management and overheating especially at turning points may cause large gas porosity in the material. On the right the micrograph exhibits a very large gas pores resulting from process instabilities due to heat accumulation.
For the resulting microstructure, the temperature gradient during part fabrication is decisive. The temperature gradient in turn depends strongly on the part’s geometry as well as the scanning strategy and cooling breaks during manufacturing. Most commonly a directed growth of long grains towards the cooling direction occurs.
Typical material properties for as build 316L in Wire Arc Additive Manufacturing
Some typical material properties for the stainless steel 316L are shown in the diagrams. All tensile values of the Wire Arc Deposition specimens exceed the required norm values defined in ASTM A276 (Standard Specification for Stainless Steel Bars and Shapes) except for elongation in horizontal direction.
An anisotropy of mechanical properties can be observed. Yield strength and ultimate tensile strength are higher in horizontal direction (perpendicular to the building direction) than in building direction. In turn, vertically oriented test specimen exhibit higher ductility. The anisotropy can be attributed to two effects. First the directed grain growth results in a strong texture of the microstructure which causes anisotropic properties. Secondly, the cooling of horizontal test bars is faster due to their larger connection area with the base plate. The faster cooling creates a finer microstructure in the horizontal test coupon compared to the vertical coupon. The fine microstructure results in higher strength and less ductility.