A Review on Cracking in Laser Additive Manufacturing of Nickel-Based Superalloys: Types, Formation Mechanisms, and Suppression Strategies

Abstract

Nickel-based superalloys (Ni-based superalloys) have attracted extensive attention in laser additive manufacturing (LAM) due to their capability to directly fabricate complex and high-performance structural components. However, the rapid melting and solidification inherent to LAM result in intense thermal cycling, which induces high residual stresses and microstructural heterogeneity within the fabricated parts. Among them, cracks, as the most destructive defects, can have a typical crack density of over five per mm2 without optimized processes. Moreover, the sudden failures of components caused by cracks account for more than 40% of the total failures of additively manufactured nickel-based superalloy components. They can rapidly expand along grain boundaries or brittle phases, significantly weakening the mechanical properties of components and causing sudden failures. To achieve highly reliable additive manufacturing components, it is essential to conduct in-depth research on the types, formation mechanisms of cracks in Ni-based superalloys, and their relationships with microstructure, residual stress, etc. This paper systematically reviews the crack characteristics and formation mechanisms of Ni-based superalloys during the laser additive manufacturing process, post-manufacturing, and service stages and comprehensively summarizes the current mainstream crack suppression strategies, specifically including process parameter optimization, residual stress regulation, alloy composition design, and subsequent post-treatment technologies, as well as incorporating emerging machine learning-assisted methods. The review aims to provide theoretical insights and technical guidance toward the development of crack-free Ni-based superalloy components fabricated by laser additive manufacturing.