This paper examines a functionally graded material, fabricated by fiber laser melting deposition and laser synchronous preheating that incrementally grades from 316L to Inconel625. The cracking behaviour, microstructure evolution and microhardness were determined as the variation of position within the graded materials. The cracks in the non-preheated samples occurred at the deposited layers from 90% 316L/10% Inconel625 to 70% 316L/30% Inconel625, and no cracks were produced in the preheated samples. Precipitation of Nb- and Mo-enrich phases was experimentally identified to be the main cause of cracking. The microstructure of the preheated samples changed from the cellular dendrites to prominent columnar dendrites, and the precipitated phases were transformed from (γ + Laves) eutectic phase to (γ + NbC) phase with the increase of Inconel625. Microhardness presented an approximate linear distribution along the gradient direction. Work shows that microstructure and internal stress can be improved by laser synchronous preheating, thereby contributing to suppress cracking for the functionally graded material.

本文研究了一种功能梯度材料，该材料是通过光纤激光熔化沉积和激光同步预热制成的，其梯度等级从316L到Inconel625。裂纹行为，显微组织演变和显微硬度被确定为梯度材料中位置的变化。在未预热样品中的裂纹发生在沉积层上，从90％316L / 10％Inconel625到70％316L / 30％Inconel625，在预热样品中均未产生裂纹。实验确定了Nb和Mo富集相的沉淀是开裂的主要原因。预热样品的微观结构从胞状树枝状转变为突出的柱状树枝状，并且随着Inconel625的增加，沉淀相从（γ+ Laves）共晶相转变为（γ+ NbC）相。显微硬度沿梯度方向呈现近似线性分布。工作表明，通过激光同步预热可以改善微观结构和内部应力，从而有助于抑制功能梯度材料的开裂。