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The initial melting quality of a high-speed laser cladding layer has an important impact on its post-treatment and practical application. In this study, based on the repair of hydraulic support columns of coal mining machines, the influence of high-speed laser cladding process parameters on the quality of Fe-Cr-Ni alloy coatings was investigated to realize the accurate prediction of coating quality. The Taguchi orthogonal method was used to design the L25(56) test. The prediction models of the relationship between the cladding process and the coating quality were established using the Random Forest (RF) and AdaBoost (Adaptive Boosting, AB) algorithms, respectively. Then, the prediction accuracy of the two models was compared, and the process parameter features were screened for importance evaluation. The results show that the AB prediction model is more accurate than the RF prediction model and more sensitive to abnormal data. The importance evaluation based on the AdaBoost model shows that the scanning speed has a great influence on the height and surface roughness of the coating. On the other hand, the overlap rate is the most important factor in controlling the dilution ratio and near-surface grain size of high-speed laser melting coatings. In addition, the micro-hardness of the coating and the thermal effect of the substrate can be effectively enhanced by adjusting the laser power and scanning speed. Finally, it was verified that the AB prediction model could accurately estimate the quality indexes of the coating with a prediction error less than 6%. The results show that it is feasible to predict the quality of high-speed laser cladding with the AB algorithm. It provides a basis for the adjustment of process parameters in the subsequent quality control process of cladding. [ABSTRACT FROM AUTHOR]

• Generation of hard phases and grain refinement in enhanced bionic units. • Bionic unit samples have good hard-soft alternating bionic structure. • Quantitative relation between distribution spacing and wear resistance is obtained. • Hard-soft bionic structure improves wear resistance by altering the wear pattern. • Adjusting the distribution spacing has a more positive effect on wear resistance. In this study, the biomimetic unit samples (BUSs) of hard-soft structure with different distribution spacings were successfully prepared by laser quenching biomimetic processing technique (LQBPT). Firstly, the microstructure, microhardness, tribological properties and wear surfaces were investigated. The BUSs had randomly oriented martensite and M 7 C 3 , and the grains were refined, resulting in favorable hard-soft structures. Compared to the untreated samples, the BUS at distribution spacing of 3 mm had excellent wear resistance. Its average friction coefficient and weight loss were reduced by 17.95 % and 40.0 %, respectively. Then, it was investigated the quantitative relationship between the distribution spacing and the wear resistance and its wear resistance mechanism. This improved wear resistance was attributed to hard-soft biomimetic structure. [ABSTRACT FROM AUTHOR]

The AlCoCrFeNi 2.1 eutectic high-entropy alloy (EHEA) has become one of the hottest research topics owing to its comprehensive mechanical properties. In this study, the AlCoCrFeNi 2.1 EHEA was fabricated via the laser powder bed fusion (L-PBF) technique, and the grain morphology, eutectic structure, mechanical properties, and deformation mechanism were investigated. The results indicate that the samples have superfine grains and nano-lamellar eutectic structures, attributable to the high cooling rate of the L-PBF process. Furthermore, the phenomenon of solute trapping was observed in the boundary of the FCC and B2 semi-cohesive phase in the nano-lamellar eutectic structure. Based on the special eutectic structure of the AlCoCrFeNi 2.1 EHEA prepared using the L-PBF technique, the samples exhibited an exceptional tensile strength of up to 1.6 GPa, accompanied by tensile ductility of over 9.5 %. The improvement of mechanical properties may be attributable to the Hall–Petch strengthening and back stress effect caused by refining the eutectic structure, whereas the growth of the nano-lamellar structure may be closely related to the solute-trapping effect. • Nano-lamellar EHEA with K–S type OR was prepared by additive manufacturing. • The L-PBF EHEA exhibited an exceptional tensile strength of up to 1.6 GPa. • The solute trapping phenomenon was observed at the boundary of nano-lamellar. [ABSTRACT FROM AUTHOR]