Investigation on the effect of laser remelting for laser cladding nickel based alloy

Abstract

Laser cladding is a recently developed additive manufacturing technique, which is widely used in remanufacturing and sustainable manufacturing fields. However, the surface roughness of laser cladding layer often fails to meet the tribological functions and assembly requirements. In order to improve the surface finish quality of laser cladding, various techniques such as manual polishing, grinding, abrasive blasting, and chemical polishing were adopted. However, these methods have certain disadvantages, such as secondary positioning and polluting the environment. Laser remelting is an eco-friendly technology, which is based on remelting of a thin surface layer and can improve surface quality without the secondary positioning. In this paper, the high-power continuous-wave carbon dioxide laser was first used for preparing laser cladding layer of nickel-based alloy and then used for laser remelting process. Design of experiments based on orthogonal arrays was employed for optimization of process parameters. Both surfaces of laser cladding and laser remelting, as well as the cross-sectional subsurface, were analyzed to investigate the variation of surface roughness. Scanning electron microscopy and energy dispersive spectrometer were used to analyze the microstructure of the remelted sample. It was shown that the average surface roughness of laser cladding layer was reduced more than 2 μm after laser remelting process. Microstructure and microhardness of laser remelting zone were investigated in order to examine the thermal effect of laser remelting processing on the laser cladding layer. It can be induced that laser remelting process is an effective method to improve the surface quality of laser cladding.

Effect of Laser Remelting on Tribological Performance of Ni-Cr-B-Si Coatings Deposited by Laser Metal Deposition

“…Standard deviation analysis indicated, at both sliding distances evaluated, approximately 20% lower variation in the remelted to as-deposited condition. Similar results are reported by García et al (2016) and Zhao et al (2018). Although as-deposited samples showed a tendency of inversely proportional relation between microhardness and wear rate, this behavior was more pronounced in the remelted coating.…”

“…Besides that, the fact that remelting posttreatment was applied immediately after the coatings deposition reduced the thermal gradient effect (tensile stresses resulting from the cooling process), contributing to this cracks elimination. In the results step (topic 3), authors will be indicated, such as Houdková et al (2014) and Zhao et al (2018), that report similar characteristics. Before and after tribological test, samples were cleaned in ethyl alcohol and dried.…”

“…In the literature, Houdková et al (2014) highlighted that during remelting process, a material portion is relocated by surface tension to the lower valleys concerning the plane. Zhao et al (2018) indicate that this phenomenon can be easily understood when it is thought that the material of the roughness peaks is driven into the valleys, filling them, leaving a smooth and more leveled surface. In this research case, the cooling cracks resultant from the deposition process probably have been filled by this phenomenon.…”

“…However, such coatings may generate, in several conditions, lack of metallurgical adhesion, extensive heat-affected zone (HAZ) and high dilution. These aspects are emphasized from well-established literature until more recent works (Toyserkani et al, 2005;Zhong and Liu, 2010;Davim, 2013;Houdková et al, 2014;D'Oliveira, 2015, 2016;Zhao et al, 2018;Sousa et al, 2020).…”

“…Besides improving metallurgical aspects, which standardizes the surface thermal cycle, generating better mechanical properties distribution along with the coating (Temmler et al, 2015). In this process, there is no removal, but only material reallocation (Yin et al, 2011;Zhao et al, 2018).…”