Author(s)

V. Ocelík, I. Hemmati, J. Th. M. De Hosson

Abstract

In this paper the influence of high cooling rate which is typical for laser surface engineering techniques, on the microstructure and properties of iron based laser deposits is studied experimentally. Four different Fe-based materials were deposited using laser cladding with powder injection at speeds that vary over a few orders of magnitudes. The microstructure of the coatings, type and quantity of their constituent phases were characterized using Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Electron Backscatter Diffraction. The hardness was measured using Vickers indentation. With increasing cooling rate, the characteristic microstructure size decreases and the inter-dendritic phases became more refined for all coatings. However, the hardness behaves differently depending on the main contributing strengthening mechanism. The effect of cooling rates on the characteristic microstructure size, phase constitution, martensitic transformation and the interplay between the various strengthening mechanisms in producing the overall hardness of the iron based deposits will be discussed and explained.

Keywords

laser cladding, microstructure, steel, hardness, electron microscopy