Improvement on Microstructure and Cracking Susceptibility of Laser-Clad Ni-Based Layers by In Situ Generation of Tantalum Carbides and Borides

Abstract:

Cracking is a serious problem in laser-clad hardfacing layers due to inhomogeneous distribution of coarse brittle phases and stress induced during rapid solidification. Tantalum carbides and borides which can form and precipitate at much higher temperatures are tentatively designed to inhibit the formation of the coarse brittle phases of chromium carbides and borides. It is found by XRD analysis that TaC, Ta4C3, TaB and Ta5B6 were formed in-situ and the coarse brittle phases were largely avoided in laser-clad Ni-based layers. It is also found that the formation sequence of these species is governed by their precipitation temperature instead of the rule determined by the standard free energy of formation. The formation of the chromium carbides and borides is inhibited due to the priority of formation of tantalum carbides and borides during rapid solidification. SEM and penetration visualization examinations show that the microstructure is markedly refined and the cracking susceptibility is significantly reduced by this method. The microhardness of the layers maintains at about 800 Hv.

• Periodical: Advanced Materials Research (Volumes 472-475)
• Pages: 239-245
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.472-475.239
• Online since: February 2012
• Authors: Hao He, Dong Sheng Wang, Er Jun Liang, Ming Ju Chao
• Keywords: Crack Susceptibility, Microstructure, Ni-Based Alloy, Tantalum Carbides and Borides

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