Abstract
A composite coating with enhanced mechanical properties including high hardness and excellent wear resistance was produced by laser cladding of mixed Ni45 and high-carbon ferrochrome powders on an ASTM 1045 steel substrate. Different quantities, ranging from 10 to 50 wt.% of high-carbon ferrochrome powder were added to the Ni45 powder to investigate the effect of mixture content on the cladding performance. The microstructure of the coatings were examined using scanning electron microscope, and the wear resistance was compared using a wear tester apparatus among the different cases. The results showed that the microstructure of the coating with 30 wt.% high-carbon ferrochrome content was mainly fine solid solution phase. With the increase of high-carbon ferrochrome content to 40 wt.% and above, cracks appeared on the cladding surface due to a large amount of chromium carbides formed during the process. The microhardness was enhanced remarkably by laser cladding the composite coating on the 1045 substrate, with 2.4 times higher than the hardness of the substrate when 30 wt.% high-carbon ferrochrome content was added. The best wear performance was achieved when the high-carbon ferrochrome content was 30 wt.%, demonstrating the smallest surface roughness and depth of wear marks. With further increased high-carbon ferrochrome content, microcracking and delamination were observed on the worn surfaces.
Highlights
Laser cladding is considered as a strategic technique since it can yield surface coatings of good performance, and often has superior properties over other hard facing techniques in terms of pureness, homogeneity, hardness, bonding and microstructure [1,2]
The formation of cracks was related to the microstructure evolution during the solidification process which will be addressed in the following discussion
For pure Ni45 and Ni45 + 10 wt.% high-carbon ferrochrome coatings (Figure 3a,b), the microstructure mainly consists of γ-Ni dendrites and some multiple eutectics
Summary
Laser cladding is considered as a strategic technique since it can yield surface coatings of good performance, and often has superior properties over other hard facing techniques in terms of pureness, homogeneity, hardness, bonding and microstructure [1,2]. Ni-based alloys, owing to their superior mechanical properties including good wettability, wear resistance, and corrosion resistance, find wide applications in industries like the aerospace, marine. Due to the relatively low contents of boron and carbon in the alloy, the hardness and wear resistance of the cladded coating is lower than Ni60. This study attempts to obtain a composite coating with improved mechanical properties including crack-free, high hardness and good wear resistance by combining the advantages of both high-carbon ferrochrome and Ni45. The benefits of adding high-carbon ferrochrome into Ni45 powder will be investigated regarding the surface cracking, changes on microstructure, micro-hardness and wear resistance etc. It is expected that the composite powders developed in this study will be a promising alternative which can be used as a high hardness and high wear resistance cladding material for various industrial applications
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