Thermal Fatigue Characteristics of a Low Carbon Steel Following Laser Surface Alloying with Cr Powder
X. Tong, F-H. Li, W-Y. Ma, X-C. Chen, M. Liu and M-J. Dai
In order to improve the thermal fatigue resistance of a melted aluminium feed launder fabricated from a low carbon steel, Q235, laser surface alloying with Cr powder was applied to strengthen the part by changing both the composition and the microstructure of its working surface layer. The cross-section morphology, phases, microstructure, microhardness and element distribution of the laser alloyed layer; along with the thermal fatigue properties of the samples were investigated. The results indicated that the Cr elements distributed symmetrically and their content increased markedly in the laser alloyed layer. Due to solid solution and dispersion effects the laser treated matrix was strengthened and hardened, which endowed the samples with higher resistance to thermal cracks initiation and propagation. As a result, the thermal fatigue resistance of the low carbon steel materials was enhanced by the laser surface alloying of the Cr powder. All samples treated by laser overlapped scanning displayed the best thermal fatigue resistance.
Keywords: Low carbon steel, Cr powder, laser surface alloying, CO2 laser, thermal fatigue, crack, feed launder