**E**ff**ect of Interlayer Cooling on the Preparation of Ni-Based Coatings on Ductile Iron**

**Yuyu He 1,2,3, Yijian Liu 1,2,3,\*, Jiquan Yang 1,2,3, Fei Xie 1,2,3, Wuyun Huang 1,2,3, Zhaowei Zhu 1,2,3, Jihong Cheng 1,2,3 and Jianping Shi 1,2,3,\***


Received: 25 March 2020; Accepted: 27 May 2020; Published: 4 June 2020

**Abstract:** In metal additive manufacturing without interlayer cooling, the macro-size of the layer itself is difficult to control due to the thermal storage effect. The effect of interlayer cooling was studied by cladding Ni-based coatings on the substrate of ductile iron. The results show that under the same process parameters, compared with non-interlayer cooling deposition, the dilution rate is better, and the thickness increase of interlayer cooling deposition is more uniform, which is conducive to controlling the macro-size of the interlayer cooling deposition. Furthermore, interlayer cooling deposition has fewer impurities and more uniform microstructures. Moreover, the average grain size is refined and the dendrite growth is inhibited, which improves the mechanical properties of the coating. Therefore, the hardness of the interlayer cooling specimens is greater than that of the non-interlayer-cooled specimens.

**Keywords:** metal additive manufacturing; nickel-based alloy; microstructure; cooling effect
