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CeO2-8YSZ (CYSZ) composite agglomerated powder was synthesized by spray drying of 20% micron-scale CeO2 powder doped with nano-ZrO2-8 mol% Y2O3 (8YSZ) powder. The effect of the binder (carboxymethyl cellulose, CMC) ratio on the properties of the composite agglomerated powder was investigated with the aid of a laser particle size tester, scanning electron microscopy (SEM) and incidental energy spectrometry (EDS). A CYSZ thermal barrier coating with a columnar structure was prepared by PS-PVD, and EDS analysis of the coating cross-section and surface was carried out. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to analyze the physical phases of the coating. The results show that agglomerated powder with high sphericity, good flowability and uniform particle size distribution can be obtained with a binder ratio of 2%, the prepared coating has a uniform distribution of Ce element, and the coating phase is basically a t-phase structure, in which Ce4+ replaces Zr4+ and enters into the ZrO2 lattice to form a homogeneous solid solution structure, showing the inhibition of the transition from t-phase to m-phase by CeO2 doping. In addition, the prepared CYSZ coating remained intact after 100 cycles of water cooling at 1100 °C, showing high thermal shock resistance.

Due to the rapid advancement in processing efficiency, high-speed laser cladding has demonstrated significant potential in the repair and protection of various substrates. In this study, we established a comprehensive evaluation model for the coating quality of Fe-Cr-Ni-based alloy with high-speed laser cladding using the analytic hierarchy process and fuzzy comprehensive evaluation method (AHP-FCE). The weights obtained through the analytic hierarchy process for forming quality, microstructure, and surface performance are as follows: WB1 = 0.1365, WB2 = 0.2385, and WB3 = 0.625, respectively. During the fuzzy comprehensive evaluation step, an evaluation level was graded while quantifying the level range through membership function judgment. By combining subjective and objective evaluations, qualitative issues were transformed into quantitative assessment methods. Through comprehensive evaluation analysis, it was concluded that the scanning speed of high-speed laser cladding had a greater impact on coating thickness compared to powder feeding speed while significantly enhancing microstructure densification. The overlap rate exerted the most influence on dilution rate homogenization of near-surface dendrites. Simultaneously, the optimal preparation technology was determined: laser power 660 W, scanning speed 14,400 mm/min, overlap rate/min. This study transforms multi-objective quality evaluation of high-speed laser cladding coatings into a single objective problem by realizing comprehensive quality quantification and providing a new method for quantitative evaluation and visualization of coating quality. [ABSTRACT FROM AUTHOR]

To solve the surface wear problem of 40Cr steel parts, incorporated with the theory of surface texture, laser phase transformation hardening technology was applied to preparate various shapes (spot and striation) of hard-soft coupling surfaces with regular distribution. Scanning electron microscopy, X-ray diffraction, friction and wear machine and ultra-depth of field microscopy were adopted to analyze the microstructure, physical phase, anti-wear performance, and wear surface morphology of the phase transformation zone. the results show that the cross-section hardness of the spot phase transformation zone is higher than the striation, with the average of (720±3) HV0.1, and the hardening layer is deeper. Martensite, Cr7C3, and Fe7C3 are generated after phase transformation. By comparing the friction coefficient between the untreated surface and the hard-soft coupling surface of 40Cr steel, the friction coefficient of the hard-soft coupling surface is inferior to 0.5 and its fluctuation is smaller which demonstrates great friction stability. In addition, the wear surface damage of the hard-soft coupling surface is small, and the reason of this is that the hard phase could resist the deformation while the soft phase could release the stress concentration and the accumulation of plastic deformations. The soft phase field is mainly pear peeling and adhesion damage, and the hard phase area is mainly small pitting pits. The 900W spot soft-hard coupling surface with the first-rate anti-wear performance. Above all, the conclusion is that the hardening phase with great plastic toughness and a certain proportion (50%) of inerratic surface distribution can markedly increase and promote the anti-wear performance of the material working surface, improve the contact surface of the fraction pair as well as stabilize the friction coefficient, this study can provide a reference for improving the surface wear of 40Cr parts. [ABSTRACT FROM AUTHOR]

In the process of laser cladding forming, the season of process parameters had a fatal influence on the quality of cladding forming. In order to solve the problems of shape control difficulty, process parameter selection and long tnal-and-error experiment period, ANSYS parametric language APDL was used to establish a three-dimensional transient model to simulate the effects of laser power, scanning speed, powder feeding amount and spot diameter on temperature and cooling rate,and the process parameters with good forming quality were optimized. Combined with three groups of experiments, the width, height and depth of the layer and the crystal phase microstructure were measured to verify the feasibility of the numerical simulation. The results show that the optimum process parameters were laser power 1 400 W, scanning speed 10 mm/s, powder feeding rate 1.8 r/min,spot daameter 2 mm, respectively. The numerical simulation results of the width, height and depth of the layer were conssstent with the experimental results, and the forming quahty of the optimized process parameters was better than that of the control group. The research results of this paper pride a valuable reference value for the problem of shape control n laser adding of IN718 nickel base superalloy. [ABSTRACT FROM AUTHOR]

Al x CoCrFeNi (x = 0, 0.2, 0.45, 0.7 and 1) high entropy alloys (HEAs) have been successfully synthesized by laser melting deposition (LMD). It is found that the microstructure of LMD-CoCrFeNi HEA with increasing the content of Al has been transformed from a single face-centered cubic (FCC) phase to mixture of FCC + BCC duplex phases, and then to body-centered cubic (BCC/B2) phases. The addition of Al (Al 0.2 , Al 0.45 and Al 0.7) remarkably improved the yield strength σ 0.2 (from 138 MPa to 185 MPa, 262 MPa and 771 MPa) and the tensile strength σ t (from 634 MPa to 675 MPa, 863 MPa and 1171 MPa) of the samples, with the prize of plasticity decrease from 46% to 45%, 41% and 11% in tension. This work provides an approach of LMD-fabricated CoCrFeNi-based HEAs with different Al addition to accommodate the microstructure and mechanical properties, and insights into the correlation of mechanical properties with the solid solution strengthening or/and the precipitation of hardening phase. • Al x CoCrFeNi (x = 0, 0.2, 0.45, 0.7 and 1) HEAs have been prepared by LMD method. • The ΔH mix and VEC are used to predict the phase stability for LMD-fabricated HEAs. • The LMD HEA has been changed from a single FCC phase to BCC phase via Al addition. • With the increase of Al amount, σ 0.2 and σ t of the HEAs under the tensile and compression test have been obvious improved. [ABSTRACT FROM AUTHOR]