Effect of flame spray distance on the adhesive characteristics of Ni-20mass%Cr layers on SCM415 substrates

Abstract

In this work, experimental results on the morphology and adhesive characteristics of flame-sprayed Ni-20 mass%Cr coating layers deposited on preheated SCM415 surfaces are presented. The flame spray distance was varied from 100 to 200mm so as to investigate the change in the adhesive strength of the deposited layers. Commercially available Ni-20 mass%Cr particles with a mean diameter of 45μm were employed in the experiments, and computational fluid dynamics (CFD) simulations using a commercial code (FLUENT) were conducted so as to estimate the temperature and velocity distributions of continuous and discrete phases before impact on the substrate. From FE-SEM images of the deposited layers, it was observed that, as the flame spray distance decreased, the metal particle morphology exhibited a splash-like pattern and a short, stretched shape. Such morphological characteristics were induced by the higher particle momentum associated with very high gas velocities. In addition, as the flame spray distance decreased, the adhesive strength between the deposited layer and the substrate increased due to the stronger momentum of the molten metal particles. © 2012 The Japan Institute of Metals.