Influence of Heat Treatment on the Microstructure and Tensile Properties of a Novel Nitrogenous Nickel-Based Deposited Metal

Abstract

Nitrogenous nickel-based deposited metal was prepared by using the gas metal arc welding (GMAW) method, and it was further subjected to solid-solution and aging heat treatment. The influence of different solid-solution temperatures on the microstructure of the deposited metal was studied, and the complete heat treatment system for the nitrogenous nickel-based deposited metal was ultimately determined. The microstructure, mechanical properties, and deformation mechanism of the nitrogenous nickel-based deposited metal in two states (as-prepared state and complete heat-treated state) were finally investigated. The results show that the microstructure of the deposited metal mainly consisted of epitaxially grown columnar grains with large grains. Petal-like Laves phases formed between the dendrites. The main deformation mechanism was the unit dislocation a/2 cut precipitation phase. After a complete heat treatment, all the Laves phases were re-melted, and nanoscale M(C,N) phases precipitated in the grains, while M23C6 phases formed at the grain boundaries. The samples showed higher yield and ultimate tensile strengths than those of the as-prepared state metal, but with reduced ductility. The deformation mechanism involved not only a/2 matrix dislocations cutting the precipitated phase, but also two a/6 Shockley incomplete dislocations, together cutting the precipitated phase to form a stacking layer dislocation.

Keywords

• heat treatment
• nitrogenous nickel-based deposited metal
• microstructure
• tensile properties
• deformation mechanism