Influence of particulate morphology on microstructure and tribological properties of cold sprayed A380/Al2O3 composite coatings

In this study,three kinds of A380/Al2O3 composite coatings were prepared by cold spray(CS)using spherical,irregular and spherical+irregular shaped Al2O3 particulates separately mixed in the original A380 alloy powders.The influence of Al2O3 particulates’morphology on the microstructural characteristics(i.e.retention of Al2O3 content in coatings,coating/matrix interfacial bonding,pore size distribution and morphology etc.)and wear performance of the coatings was investigated by scanning electron microscopy(SEM),X-ray computed tomography(XCT)and 3-D optical profilometry.Results indicated that the spherical Al2O3 showsobvious tamping effect during deposition process.As a result,the interfaceshowedawavy shape while the matrix and particulates were mechanical interlocked with much improved adhesion.In addition,the porosity of the coating was minimized and the pores exhibited curved spherical structure with reduced dimensions.The irregular Al2O3 particles predominantly displayed the embedding effect together with fragmentation of Al2O3 particulates.Consequently,poor coating/matrix interfacial bonding,high porosity and the formation of angular-shaped pores were resulted in the coating.Dry sliding wear tests results revealed that the wear resistance of the coating is directly related with the retained content of Al2O3 in the coating.The coating containing irregular Al2O3 particulates displayed superior wear performance with its wear rate one seventh of that of the pure A380 alloy coating.The coating containing both kinds of Al2O3 particulates showed mixed characteristics of above two kinds of Al2O3 composite coatings.

Effect of Ni Interlayer on Cavitation Erosion Resistance of NiTi Cladding by Tungsten Inert Gas(TIG)Surfacing Process

The NiTi cladding with/without Ni interlayer was prepared on stainless steel(SS) by tungsten inert gas(TIG) surfacing process,aiming at achieving good cavitation erosion resistance.The ranking according to the cavitation erosion resistance is NiTi plate> NiTi-Ni-TIG cladding> NiTi-TIG cladding> SS.The better cavitation erosion resistance of NiTi-TIG and NiTi-Ni-TIG claddings than SS substrate is due to their higher micro-hardness and superelasticity.Furthermore,the existence of Ni interlayer can decrease the amount of brittle intermetallic compounds,such as Fe2 Ti,and inhibit the crack generation,which results in the higher cavitation erosion resistance of NiTi-Ni-TIG compared with NiTi-TIG cladding.Thus,the cavitation erosion resistance of NiTi cladding prepared by TIG surfacing process can be improved by employing Ni interlayer.

Effects of Dissimilar Alumina Particulates on Microstructure and Properties of Cold-Sprayed Alumina/A380 Composite Coatings

In this study,alumina/A380 composite coatings were fabricated by cold spray.The influence of alumina particulates,morphology(spherical and irregular)and content on the deposition behavior of the coatings(including surface roughness,surface residual stress,cross-sectional microstructure and microhardness)was investigated.Results revealed that the spherical alumina mainly shows micro-tamping effect during deposition,which result in remarkable low surface roughness and porosity of the coatings.In addition,very low deposition efficiency and good interfacial bonding between the coating and the substrate were achieved.For irregular alumina particles,the embedding of ceramic particulates in the coating was dominant during deposition process,resulting in high retention in the final deposit.However,it showed limited influence on porosity,surface roughness and interfacial bonding of the deposit.The coatings containing irregular alumina particulates exhibited much higher microhardness than those containing spherical alumina due to the higher load-bearing capacity of deposited alumina.

Feedforward Control for Wind Turbine Load Reduction with Pseudo-LIDAR Measurement

A gain-scheduled feedforward controller, based on pseudo-LIDAR （light detection and ranging） wind speed measurement, is designed to augment the baseline feedback controller for wind turbine＇s load reduction in above rated operation. The pseudo-LIDAR measurement data are generated from a commercial software- Bladed using a designed sampling strategy. The nonlinear wind turbine model has been simplified and linearised at a set of equilibrium operating points. The feedforward controller is firstly developed based on a linearised model at an above rated wind speed, and then expanded to the full above rated operational envelope by employing gain scheduling strategy. The combined feedforward and baseline feedback control is simulated on a 5MW industrial wind turbine model. Simulation studies demonstrate that the proposed control strategy can improve the rotor and tower load reduction performance for large wind turbines.

A viable approach to repair neutron shielding B_(4)C/6061 Al composite sheets through cold spray and hot rolling co-treatment

Cold spray(CS) is considered as a new type of repairing technique for restoration or remanufacturing of a wide range of unserviceable engineering components due to its unique ‘cold’ characteristic. In this work, a viable repairing approach i.e. "cold spraying followed by hot rolling post-treatment" was successfully applied to restore defective neutron shielding B_(4)C/6061 Al composite plates. Scanning electron microscopy(SEM) and electron backscatter diffraction(EBSD) results revealed that the coating-substrate interface is in a good bonding state without micro-cracks. Hot rolling post-treatment resulted in improved microstructure of the as-sprayed deposit with more uniform distribution of B_(4)C particles in the matrix.Moreover, well bonded splat boundaries and strain free Al grains were evolved in the matrix due to enhanced splat deformation and continuous dynamic recrystallization(CDRX). Three-point bending test results revealed that the strength of the repaired material is at par with the in-service plates. The findings of this work could be considered as a great stride to further extend possible applications of CS for repairing engineering structural components.

Erratum to “Influence of particulate morphology on microstructure and tribological properties of cold sprayed A380/Al_(2)O_(3) composite coatings” [J. Mater. Sci. Technol. 44 (2020) 9-18]

In our recently published article,“Influence of particulate morphology on microstructure and tribological properties of cold sprayed A380/Al_(2)O_(3) composite coatings”[Journal of Materials Science&Technology 44(2020)9-18]”,Fig.5 got repeated inadvertently.This led to the displacement in the order of Figs.6 and 7 one step ahead.Consequently,the captions in Figs.6-8 in the manuscript were mismatched.Further,it caused the omission of Fig.8 described in the original manuscript.This erratum corrects the order of Figs.6-8 along with their corresponding figure captions.This erratum does not affect the conclusions of that paper.The publisher would like to apologize for any inconvenience caused.