Tensile Properties, Microsctructure and Microhardness Analysis of Directly Deposited Waspaloy by Gas Tungsten Arc Welding
Nur Izan Syahriah Hussein, Mohamad Nizam Ayof, Mohd Amri Sulaiman, Graham McCartney and Ian Pashby
Solidification of Waspaloy during Direct Metal Deposition (DMD) by Gas Tungsten Arc Welding (GTAW) process leads to dendritic segregation and interdendritic carbide formation which can strongly influence the mechanical properties of the deposited structure. Heat treatment of DMD parts is the principal means of altering the microstructure and optimizing the mechanical properties. Thus, the main aim of the present study is to investigate the effect of heat treatment on microstructure, microhardness and tensile behaviour of the Waspaloy produced by DMD. The effects of sample location at the transverse directions (parallel to the multilayer wall height) were investigated. The resulting microhardness and tensile test data were compared to the wrought Waspaloy base plate as a baseline. The tensile fracture surfaces were examined to provide insight into fracture mechanisms. The results show that the microhardness and tensile properties of the arc directly deposited Waspaloy depend strongly on the microstructure, which, in turn, is controlled by the deposition process and following the heat treatment conditions. This is particularly the case for properties such as the 0.2% proof stress, which is sensitive function of the distribution of the γ’ phase. Solution treatment and double ageing definitely can improve the tensile properties of the deposited Waspaloy. Fracture surfaces of samples tested transverse to the deposition height show fracture by microvoid coalescence which initiated by interdendritic particles.