To reveal the effect of laser remelting on the high-temperature oxidation resistance of high-entropy alloy (HEA) coating, an AlCoCrFeNi HEA coating was prepared on AISI 1045 steel by plasma spraying ...technology and then remelted by laser remelting process. The microstructure of the coatings before and after remelting was characterized, and oxidation experiment was carried out at 900 °C for 100 h. The results showed that, after laser remelting, the porosity of AlCoCrFeNi HEA coating decreased from 4.8 % to 0.3 %. Moreover, the phase compositions of the coating after remelting were the same as that before remelting, which were still dominated by a single BCC solid solution structure. After oxidation, the oxidation weight gain of the remelted coating was slightly greater than that of the as-sprayed coating. Nevertheless, uniform and dense multilayer oxide films were formed on the remelted coating surface, leading to the lower oxygen content in the remelted coating and at the interface of remelted coating/substrate. Therefore, laser remelting can effectively improve the ability of AlCoCrFeNi HEA coating to hinder oxygen at high temperature and prevent the substrate from oxidation.
•Laser remelting improved the coating's ability to hinder oxygen at high temperature.•Uniform and dense multilayer oxide films were formed on the remelted coating surface.•The order of oxides formation and distribution of different oxide films were discussed.•The oxidation behavior was studied from the aspects of oxidation thermodynamics and kinetics.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
High entropy alloys have promising wear, oxidation, and corrosion properties compared to conventional alloys and superalloys. In the present study, CrCuFeNiAl0.5 and CrCuFeNiAl0.5Si0.5 alloys were ...prepared using a traditional powder metallurgy process and then remelted the surfaces via laser. The laser remelting (LR) process gains a denser and more homogeneous surface to alloys. Pressureless consolidated and laser-remelted specimens were subjected to wear, corrosion, and oxidation tests. In the wear tests, it was observed that the wear resistance of Si-containing samples was better due to higher hardness. However, the laser remelting process has mostly increased rather than reduced wear losses. The less volume loss of laser-melted samples was attributed to the almost pure Cu in its content. There is little difference among all samples in electrochemical corrosion measurements. The formation of a fragile passivation layer was observed in potentiodynamic polarization curves of CrCuFeNiAl0.5Si0.5 and LR-CrCuFeNiAl0.5Si0.5 alloys. The alloy with the best corrosion resistance is CrCuFeNiAl0.5Si0.5, whose icorr value is 0.936 × 10−6 A/cm2. After high-temperature oxidation tests, the CrCuFeNiAl0.5 alloy exhibited the worst oxidation performance due to not forming a protective oxide layer on the surface, while LR enabled the protective oxide scale in a short oxidation time. The presence of Si in this alloy relatively enhances the oxidation resistance. The best oxidation performance was observed in LR-CrCuFeNiAl0.5Si0.5 due to the forming of a protective Al2O3 layer during the oxidation tests.
•Laser remelting significantly enhanced the microstructure and phase distribution.•Si addition increased hardness, wear, corrosion and oxidation resistance.•Cu-rich regions caused wear losses to be different than expected.•The addition of Si affects the electrochemical properties and passive film formation•The laser remelting process and Si addition provide alumina scale after oxidation.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Al2O3-40%TiO2 coating fabricated by plasma spraying on carbon steel substrate were remelted by laser, and the effect of laser remelting on microstructure and wear resistance of plasma sprayed ...Al2O3-40%TiO2 coating were studied. The microstructure and phase composition of plasma sprayed and laser remelted coatings were analyzed using scanning election microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction(XRD). The micro-hardness and adhesion strength of two coatings were measured using micro-hardness tester and electronic universal tensile testing machine. The wear resistance of two coatings was tested through a slurry rubber wheel abrasion test machine, and the wear behaviour was also studied by SEM.
The results show that metastable phase γ-Al2O3 in coating is completely transformed into stable phase α-Al2O3 after laser remelting. The laser remelted coating becomes much denser, and then its microhardness and adhesion strength have been greatly improved. The laser remelted coating exhibits better wear resistance compared to the plasma-sprayed coating, and the main wear mechanism responsible for wear was microcrack and fracture wear.
•Laser remelting can reduce the pores and microcracks and eras the lamellar defect.•The microstructure becomes homogenous and compact after laser remelting.•Laser remelting can greatly improve the wear resistance of the plasma sprayed coating.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To improve fretting wear resistance, bio-ceramic coatings were successfully fabricated on TC6 alloy substrates using a combination of laser remelting (LRM) and micro-arc oxidation (MAO). The surface ...morphology, composition, and residual stress distribution of the coatings were characterized using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, ultra-deep field three-dimensional microscopy, and X-ray stress analysis. The influence of LRM pretreatment on the fretting wear behaviour of MAO bioceramic coatings was investigated. The LRM pre-treatment did not change the phase composition of the MAO coatings, which were all composed of Al2TiO5, rutile TiO2, and anatase TiO2 phases. However, increasing the content of the rutile TiO2 phase from 68 to 89% improved the uniformity and density of the coatings and decreased the porosity by 2.8%. The fretting wear test results showed that the LRM pretreated MAO coating exhibited the best performance against fretting wear in a simulated body fluid environment. In this case, the fretting wear mechanism was attributed to slight delamination and fatigue wear.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
High pressure single-crystal turbine blades made from nickel-based superalloys can withstand temperatures of up to 1100°C due to their superior creep and fatigue properties compared to ...polycrystalline material. However, these parts undergo erosion and cracking due to the extreme conditions they are subject to in the engines of commercial airplanes. Since there is no effective method of repairing these expensive parts, while maintaining the necessary microstructure, the need to develop and establish a reproducible process is of high importance. The process of Laser Material Deposition (LMD) has shown promising results in the building-up of single-crystal or directionally solidified structures, while laser remelting has been shown to extend this monocrystalline height. By combining the two processes, this study aimed to deposit and remelt single-crystal structures on substrates of the nickel-based superalloys CMSX-4 and turbine blade tips of PWA 1426. Experiments were carried out to establish laser parameters that resulted in a monocrystalline microstructure. This study showed that the combination of cladding and remelting can be used to deposit single-crystal structures and was able to establish a reproducible laser process to this effect. The results obtained indicate that the process is a promising candidate for the repair of turbine blade tips and warrants further research into the microstructure and thermomechanical properties of the repaired areas.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Laser remelting tests were conducted on the Fe-based clad layer under different remelting time and remelting power conditions.•The morphological characteristics of the Fe-based clad layer after ...remelting under different remelting time and remelting power conditions were investigated.•The microhardness of the Fe-based clad layer after remelting under different remelting time and remelting power conditions was investigated.•The wear resistance, wear rate and wear mechanism of the Fe-based clad layer after remelting under different remelting time and remelting power conditions were investigated.•When the remelting time is 1 and the remelting power is 650 W, the clad layer has high microhardness and outstanding wear resistance.
Laser remelting is a processing technique to improve the quality of forming. The remelting power and the remelting time are the key factors affecting its processing quality. Laser remelting tests were conducted on Fe-based clad layers with different remelting power and remelting time, and the morphological characteristics of each clad layer was investigated by laser microscopy. The microhardness, wear resistance and wear mechanism of each clad layer were investigated by Vickers microhardness tester and reciprocating friction and wear tester, respectively. The results show that an increase in remelting power or remelting time leads to a decrease in clad height and an increase in melting pool depth, clad width and dilution rate. When the remelting time is 1 and the remelting power is 650 W, the clad height is higher than that of YCF102 clad layer, although the melting pool depth, clad width and dilution rate of the clad layer are greater than that of YCF102 clad layer. In addition, an increase in remelting power or remelting times leads to a decrease in the microhardness of the clad layer and a deterioration in the wear resistance, which leads to an increase in the wear rate, but does not change the trend of microhardness, wear resistance and wear rate. Neither the increase in remelting power nor the remelting time leads to a change in the wear form, but causes the wear between the clad layer and the grinding ball to become more intense. The clad layer with 1 remelting time and 650 W remelting power has higher average microhardness and more outstanding wear resistance than the YCF102 clad layer.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Display omitted
•Optimize the process parameters for LPBF-IN718 based on the bidirectional scanning strategy.•Clarify the impacts of hatch spacing on the microstructure and texture of ...LPBF-IN178.•Present the selection effect of laser remelting on the growth texture of LPBF-IN718.
This study investigated the effects of hatch spacing and laser remelting on microstructure and growth texture of IN718 superalloy fabricated via laser powder bed fusion (LPBF) based on the bidirectional scanning strategy. A crystallographic lamellar microstructure (CLM) with a 〈001〉 // the building direction (BD) growth texture in the center layer was obtained. The increase of hatch spacing can influence the intensity of 〈001〉 // BD growth texture in the center layer and deflect the 〈011〉 oriented dendrites in the overlapping layer to the scanning direction. Meanwhile, with the increase of hatch spacing, the primary dendrite arm spacing increases, and morphologies of the interdendritic precipitated Laves phases change from discrete dots to chains. The selection effect of laser remelting was discovered, which works as the “selector” for preferential orientation grains. Through several times of interlayer laser remelting, the grains with preferential orientations are selected by competitive growth. Laser remelting can also eliminate the stray grains and dendrites on the top of the molten pool and improve the heat input. Therefore, the epitaxial growth of 〈001〉 // BD columnar grains in the center layer is promoted. Based on the optimized hatch spacing and the laser remelting process, a 〈001〉 // BD near directional solidification structure is obtained.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Laser remelted AlCrFe2Ni2 medium entropy alloy showed nano-size weave-like microstructure with alternated ordered B2 and disordered BCC phases.•The rapid cooling rate of laser remelting promoted the ...refinement of grains.•The yield strength of remelted medium entropy alloy derived from nano-indentation tests could reach 1647.2 MPa.•Dislocation and precipitation are dominant strengthening mechanisms in the laser remelted medium entropy alloy.
A Co-free as-cast AlCrFe2Ni2 medium entropy alloy (MEA) with multi-phases was remelted by fiber laser in this study. The effect of laser remelting on the microstructure, phase distribution and mechanical properties was investigated by characterizing the as-cast and the remelted AlCrFe2Ni2 alloy. The laser remelting process resulted in a significant decrease of grain size from about 780 μm to 58.89 μm (longitudinal section) and 15.87 μm (transverse section) and an increase of hardness from 4.72 ± 0.293 GPa to 6.40 ± 0.147 GPa (longitudinal section) and 7.55 ± 0.360 GPa (transverse section). It was also found that the long side plate-like microstructure composed of FCC phase, ordered B2 phase and disordered BCC phase in the as-cast alloy was transformed into nano-size weave-like microstructure consisting of alternating ordered B2 and disordered BCC phases. The mechanical properties were evaluated by the derived stress-strain relationship obtained from nano-indentation tests data. The results showed that the yield stress increased from 661.9 MPa to 1347.6 MPa (longitudinal section) and 1647.2 MPa (transverse section) after remelting. The individual contribution of four potential strengthening mechanisms to the yield strength of the remelted alloy was quantitatively evaluated, including grain boundary strengthening, dislocation strengthening, solid solution strengthening and precipitation strengthening. The calculation results indicated that dislocation and precipitation are dominant strengthening mechanisms in the laser remelted MEA.
Display omitted
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Crack-pore, residual stress, dimensional error occur in laser based remanufacturing.•Successive laser remelting can mitigate these partly and improve fatigue strength.•Techniques to predict, ...monitor, control laser based deposition have been reviewed.•Hybrid additive manufacturing can give dimensional stability and surface finish.•Artificial intelligence can significantly assist laser based remanufacturing.
Increased focus on reduction of impact on the environment has put the aspect of remanufacturing in the spotlight, and remanufacturing of high-value engineering components is gradually becoming a mainstream practice. Out of different alternatives, laser-based deposition has been the central choice for remanufacturing, thanks to its accuracy, and precision. However, considering the complex process physics involved in laser-based remanufacturing processes, it is essential to establish the reliability of the process so that certifiable remanufactured parts can be produced. This work provides a comprehensive analysis of the issues encountered during laser-based remanufacturing, and the different approaches to address them. Apart from covering the state-of-the-art of remanufacturing by laser-based deposition, this article also discusses tools like deep learning, and digital twin which are still in their early phases in terms of applications in the remanufacturing domain.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The study is aimed to analyse the comparative behaviour of the high-temperature abrasive wear of H13 steel surfaces modified by laser melting and cladding with Stellite 6 and Stellite 6 + 30 wt% WC. ...3-body abrasive tests were conducted at room temperature, 450 °C, 550 °C, and 650 °C. The microstructural evolution, microhardness, wear surface morphology and mechanisms, and various phases formed during laser surface modifications were also studied. The laser remelting of H13 steel surface increased its room temperature microhardness to 750 ± 35 HV0.01, whereas laser cladding of Stellite 6 powder yielded hardness of around 600 ± 20 HV0.01 in the clad layer; and Stellite 6/WC composite clad layer had marginally higher hardness than the Stellite 6 clad layer in the matrix and much higher hardness of ~3000 HV0.01 at the sporadically distributed WC particle sites. Though the room temperature microhardness of laser remelted H13 surface is the highest, the volumetric wear loss in it was comparable to that of the Stellite 6 cladding. However, Stellite 6/WC composite layer recorded a relatively less volumetric loss as WC particles resisted the abrasive wear. With increasing temperature, the wear loss in laser remelt surfaces increased at a fast rate, while that in Stellite 6 and composite clad layers varied marginally with no definite trend. Overall, Stellite 6/WC composite cladding performed better than others in the current temperature range.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
