Laser-induction Hybrid Cladding Research Articles

Microstructure, wear and friction behavior of CoCrAlTaY-xCNTs composite coatings deposited by laser-induction hybrid cladding

Microstructure, wear and friction behavior of CoCrAlTaY-xCNTs composite coatings deposited by laser-induction hybrid cladding

Effect of temperature on the oxidation behavior of Al2O3 reinforced CoCrAlYTa coating by laser-induction hybrid cladding

The 2 wt% Al2O3 reinforced CoCrAlYTa coatings (referred to as 2Al2O3-CoCrAlYTa) were manufactured by laser-induction hybrid cladding. And the oxidation behavior of the coatings was investigated using a thermogravimetric analyzer (TGA) at different oxidation temperatures (950 °C, 1000 °C, 1100 °C, and 1200 °C) in an air atmosphere with a test time of 200 min. The composition and microstructure of the oxide scales formed at different temperatures were characterized and investigated. Additionally, the microstructure evolution of the coating, failure mechanism of the oxide scales, and elemental diffusion at the different temperatures were also discussed. It was found that after oxidation, Al depleted zones appeared in the 2Al2O3-CoCrAlYTa coatings. When oxidation temperature was 950 °C, fine-equiaxed oxide grains were formed on the coating. Moreover, at 950 °C, 1000 °C, and 1100 °C, the oxide scales were intact, and no large voids were found in the oxide scale/coating interface. As the temperature reached 1200 °C, the oxide scale formed on the surface of the coating became thicker and consisted of an outer layer of fine equiaxial crystals and an inner layer of coarse columnar crystals, and large voids developed at the oxide scale/coating interface, causing the oxide scales to delaminate from the coating.

Investigation on the Ni60-WC composite coatings deposited by extreme-high-speed laser-induction hybrid cladding technology: Forming characteristics, microstructure and wear behaviors

In this work, Ni60-WC composite coatings with 35 wt% WC (Ni65-WC35), 50 wt% WC (Ni50-WC50) and 65 wt% WC (Ni35-WC65) were deposited by the extreme-high-speed laser-induction hybrid laser cladding technology (EH-LIHC), and the forming characteristics, microstructure, hardness and wear behaviors were investigated systematically. Results indicated that all the EH-LIHCed Ni60-WC coatings displayed low-roughness surfaces and even-distributed WC particles, where the dilution ratio and WC's heat-loss increased with the rise of induction heating temperature (T) and WC's content. Crack-free single-layer Ni60-WC coatings could be obtained at T ≥ 600 °C, whereas some micro-cracks were inevitably induced during the multi-layer depositions. The WC particles mainly presented the decomposition/ dissolution-diffusion, collapse-dissolution and decomposition/dissolution-precipitation heat damages, corresponding to the W-rich dendritic/wing-like/filamentary structures, dendritic facet structures and blocky facet structures on the metal matrix, respectively. Under both loading forces of F = 50 N and 80 N, the wear rates Ni60-WC composite coatings presented the order of Ni35-WC65 < Ni65-WC35 < Ni50-WC50. Spalling of the matrix, cracking and crushing of the WC particles were detected on all worn surfaces. The Ni35-WC65 coating possessed the highest contents of WC particles and facet carbides, making its damage threshold and wear resistance enhanced significantly. Nonetheless, the wear debris in Ni65-WC35 coating had formed a metal layer covering on the worn surface, helping to alleviate the damage of the beneath WC particles significantly, therefore it possessed lower wear rate than that of Ni50-WC50 coating.

Comparison on the Ni60 Coatings Deposited by Extreme-High-Speed and Conventional Laser-Induction Hybrid Cladding Technologies: Forming Features, Microstructure and Wear Behaviors

Comparison on the Ni60 Coatings Deposited by Extreme-High-Speed and Conventional Laser-Induction Hybrid Cladding Technologies: Forming Features, Microstructure and Wear Behaviors

Effect of Al2O3 content on the high-temperature oxidation behaviour of CoCrAlYTa coatings produced by laser-induction hybrid cladding

The microstructure and isothermal oxidation behaviour of CoCrAlYTa coatings containing different Al2O3 contents produced by laser-induced hybrid cladding (LIHC) were investigated. The results showed that the addition of Al2O3 particles to the CoCrAlYTa coatings reduced the critical concentration of Al due to the increased diffusion coefficient of Al, which promoted the formation of continuous and complete Al2O3 scales. However, the growth of tantalum oxide in the CoCrAlYTa coating resulted in cracking of the surrounding oxide scales. Interestingly, a CoCrAlYTa coating made of the optimal content of 2 wt% Al2O3 formed an oxide scale with good compactness after high-temperature oxidation.

Microstructure, Wear and Friction Behavior of Cocraltay-Xcnts Composite Coatings Deposited by Laser-Induction Hybrid Cladding

Microstructure, Wear and Friction Behavior of Cocraltay-Xcnts Composite Coatings Deposited by Laser-Induction Hybrid Cladding

Comparative studies on the Ni60 coatings deposited by conventional and induction heating assisted extreme-high-speed laser cladding technology: formability, microstructure and hardness

Extreme-high-speed laser cladding technology (EHLA), which can deposit coatings with high efficiency and excellent surface accuracy, has attracted great attentions recently. However, due to the high cooling rate and large overlapping ratio therein, the cracking tendency of hardfacing coatings cannot be reduced but even enlarged compared with that in the traditional laser cladding process, which limits its wider applications significantly. Aiming to above problems, an extreme-high-speed laser-induction hybrid cladding technology (EH-LIHC) was proposed in this paper. The Ni60 coatings were deposited by EHLA and EH-LIHC, and the formability, cracking behaviors, microstructure and microhardness distributions of different coatings were studied systematically. Results indicate that Ni60 coatings with low surface roughness of Ra <15.0 μm can be deposited by both EHLA and EH-LIHC. However, dense cracks form in the Ni60 coating by EHLA, whereas they are reduced significantly by EH-LIHC and eliminated absolutely at induction heating temperature T = 500 °C. Moreover, the increase of T in EH-LIHC shows little effect on the coating's dilution although the diffusion of Fe element is enlarged. Composite structures of the proeutectic γ-Ni dendrites, γ-Ni + Ni3B eutectics, and Cr7C3+CrB precipitates are generated in all Ni60 coatings. The grain size of the coating, and the content and distribution uniformity of the precipitates therein are all enhanced with the increase of T. Comparatively, its microhardness is little influenced, which is about HV900-960 at T = 300 °C∼500 °C, slightly lower than that in Ni60 coating by EHLA (HV970-1000). The EH-LIHC technology proposed in this paper provides a promising approach for preparing crack-free hardfacing coatings with high efficiency and high precision.

Laser-induction hybrid cladding of different coatings on rail surface: Microstructure, wear properties and contact fatigue behaviors

In this paper, Ni-Cr-Fe, 17-4PH and 18Ni300 alloy coating were deposited on the rail surface by laser-induction hybrid cladding (LIHC), respectively. The microstructure, microhardness of different coatings, and their influences on the wear properties and contact fatigue behaviors of rails were studied systematically. Results indicate that the as-deposited Ni-Cr-Fe coating is constituted of the dendrite structure, and the as-deposited 17-4PH and 18Ni300 coating mainly consist of the lath martensite structure. The microstructure and microhardness of Ni-Cr-Fe coating are little influenced by the in-situ thermal cycling in LIHC process, whereas the grain size and precipitates’ content in 17-4PH and 18Ni300 coating are affected significantly, making the microhardness therein increased along the depth direction. Compared with the untreated rail, the wear rate and plastic deformation (PD) depth of rails with 17-4PH and 18Ni300 coating are both decreased significantly, while the contact surface damage is alleviated simultaneously. Especially for that with 18Ni300 coating, the decreased proportions are as high as 40.2% (mass wear rate), 60.1–81.2% (dimensional wear rate) and 78.7% (plastic deformation depth), respectively. By contrast, the wear rate of rail with Ni-Cr-Fe coating is increased conversely than that of the untreated rail although its microhardness is 32% higher. Therefore, the LIHC deposited 18Ni300 coating is a competitive choice for repairing the rail in engineering.

Effect of induction post-heating temperature on the morphology, microstructure and mechanical performance of the heat affected zone in laser-induction hybrid cladding of full-scale rail

Abstract In the present work, the laser-induction hybrid cladding technology with induction post-heating (post-LIHC) was utilized to deposit coatings on the full-scale rail surface, and the effects of different induction post-heating temperature on the morphology, microstructure and mechanical performance of the heat affected zone (HAZ) were first in-depth analyzed. Results indicate that with the increase of the average induction post-heating temperature (Ta) in post-LIHC, the microstructure of the HAZ first transforms from the fine acicular martensite structure to the composite structure of martensite and pearlite, then changes to the pure pearlite structure, and finally retransforms to the coarse martensite structure. Especially, the morphology of the “Martensite Zone” (MZ) in HAZ undergoes three remarkable change with Ta increasing: “flat-U-shaped” → “flat-W-shaped” → “vanished” → “flat-V-shaped”. Under the induction post-heating window of Ta = 508 °C ~ 565 °C, not only the MZ in HAZ can be inhibited absolutely, but also fine pearlite with much lower interlamellar spacing, smaller grain size and higher grain misorientation forms instead, making the strength and toughness are both enhanced significantly than the other three type HAZs and the rail substrate. In addition, increasing the induction post-heating temperature within the window of Ta = 508 °C ~ 565 °C can increase the interlamellar spacing and reduce the ferrite grain misorientation of the pearlite structure in HAZ, but has no obvious effect on the grain size therein.

Influence of Al2O3 particles on the tribological properties of CoCrAlYTa coating produced by laser-induction hybrid cladding

The influence of Al2O3 addition on the microstructure, mechanical and tribological properties of CoCrAlYTa coating produced by laser-induction hybrid cladding was systematically investigated. The results show that the coatings exhibit high metallurgy quality with no obvious defects, and mainly consist of γ, β and TaC phases. In the cladding process, a part of O element exists in the TaC and increases with the increased Al2O3 content, while the other exists in the form of Y2O3 due to low Gibbs free energy. As the Al2O3 content increases, the volume fraction of β phase (Vβ) changes from 23.82 vol% to 67.72 vol%, and leading to the microhardness of coating increased from 515.15 HV to 610.17 HV. Meanwhile, the wear rate of coating increases with the Vβ in a relationship of y = −5.97x+110.65, due to a fact that the wear mechanism changes from adhesive wear to microcutting.

Comparison on the wear properties and rolling contact fatigue damage behaviors of rails by laser cladding and laser-induction hybrid cladding

In this paper, the wear properties and rolling contact fatigue (RCF) damage behaviors of the rails with Ni-based coatings deposited by laser cladding (LC) and laser-induction hybrid cladding (LIHC) are studied comparatively by roll–sliding contact tests. The results indicate that the RCF damage characteristics of the rail rollers by both LC and LIHC are almost same at the maximum contact stress σmax ≤ 800 MPa, while the wear rate of rail roller by LC is slightly lower. However, when the maximum contact stress increases to σmax ≥ 1230 MPa, the coatings and heating affected zone (HAZ) at the contact edge of the rail roller by LC spall and fracture severely, leading to much higher wear rate and much poorer smoothness than that by LIHC. Thus, compared with LC technology, LIHC technology can reduce the wear rate and contact fatigue damage extent of rails at higher contact stress, and thereby maintain the surface profile and smoothness better.

Effect of laser cladding and laser-induction hybrid cladding coatings on the bending properties and fracture behavior of rails

Laser cladding (LC) and laser-induction hybrid cladding (LIHC) technologies, with low dilution, low deformation and high deposition efficiency, have attracted a lot of notices in repairing and hard-facing the full-scale rail. However, the cladded coatings with different microstructure and properties will also affect the bending stress distributions of rails during service, which may lead to the rails' failure and fracture. In this paper, the bending properties and fracture mechanisms of rails deposited by LC and LIHC were studied systemically by the three-point bending tests coupled with finite element method simulations (FEMS). The results indicate that the ultimate bending strength (UBS), fracture strain (εf) and fracture work (W) of the specimen by LIHC are about 1.35, 4.28 and 7.70 times of that by LC correspondingly. The dramatically difference is mainly caused by the heat affected zones (HAZs) induced by different technologies. Under the bending stress, both the maximum stress and initial damage of the specimen by LC generate in the HAZ, while the cracks extend intergranularly in HAZ and lead to the rapid overall instable fracture. Oppositely, the initial damage of the specimen by LIHC originates from the surface on the tension side where the maximum stress generates, and the HAZ by LIHC is proved to be able to promote both the bending strength and fracture toughness of the rail. On the other hand, the thickness and properties of the cladded coatings are the main factors affect the bending properties of specimens by LIHC. When the parameters are chosen suitably, both the yielding strengths and UBSs of specimens by LIHC are even higher than that of the rail substrate, which means LIHC can adjust the rail's performances reasonably while prevent the rail from bending fracture.

A comparison of microstructure and mechanical properties of laser cladding and laser-induction hybrid cladding coatings on full-scale rail

With the rapid development of high-speed and heavy-haul trains, the surface damages of rails are becoming more and more severe, and how to promote the surface strength of the rail and prolong its service life with high efficiency are becoming extremely important. Laser cladding (LC), with small heat affected zone (HAZ) and low dilution, is a promising novel way to hardface and repair the rail. However, there are two great barriers for the traditional LC to apply on full-scale rails: one is how to prevent the coating from cracking under the rapid heating and cooling cycle; the other is how to eliminate the martensite structure in HAZ, which may threaten the safety of railway transportation due to its high hardness and low fracture toughness and usually be forbidden in almost all the Railway Standards over the world. In this paper, laser-induction hybrid cladding (LIHC) was innovatively proposed to deposit Ni-based coatings on a full-scale rail. The cracking behaviors, microstructures and mechanical properties of the coatings and HAZs by LC, LIHC with induction pre-heating (pre-LIHC) and LIHC with induction post-heating (post-LIHC) were studied systemically. The results indicate that the cracking and martensite transformation occurred in the HAZ can only be prevented by post-LIHC, where fine pearlite with smaller pearlite block size and lower interlamellar spacing formed instead. Therefore, the abrupt change of microstructure and mechanical properties in the HAZ could be avoided by post-LIHC, and the hardness, strength and toughness of the rails can be improved significantly. The post-LIHC technology shows the potentiality to hardface and repair the full-scale rail.

Wear resistance of nickel-based alloy coating formed by multilayer laser cladding

Different thickness coatings formed by multilayer laser cladding are widely employed in laser repairing and the wear resistance of them are concerned. Multilayer nickel-based alloy were fabricated on the surface of low alloy steel by laser-induction hybrid cladding. Orthogonal analysis was used to evaluate the influence of the number of coating layers, load and relative velocity on the wear resistance of the coating. Wear loss and friction coefficient were set as the evaluate indexes. Microstructure, element distribution and phase composition were investigated by optical microscope, energy dispersive spectrometer (EDS) and x-ray diffractometer (XRD). Microhardness and worn surface of coatings were also tested.The results showed that the number of coating layers had an effect on the wear resistance of nickel-based coating. With the increase of coating thickness, more uniform was happened to the crystal grain. The nickel-based alloy coating was mainly composed of Cr23C6, Cr7C3, CrB, FeNi3 and Fe23(C, B)6. The lowest hardness was shown in the single-layer coating with an average value of 818.0 HV0.2. The average hardness of the two-layer coating and three-layer coating was 6.88% and 16% higher than that of the single-layer one, respectively. The cross-sectional area of the worn surface was (0.64 ∼ 2.3) × 10−3 mm2 and the distribution of them was consistent with the distribution of wear loss. The wear mechanism of nickel-based coating in this friction system was abrasive wear. The good wear resistance of the nickel-based alloy coating was mainly due to the presence of dense fine crystal grain and hard phase.

Formation and properties of a self-assembled Cu-Fe-Ni-Cr-Si immiscible composite by laser induction hybrid cladding

A self-assembled Cu-Fe-Ni-Cr-Si immiscible composite with a bilayer structure was produced by laser induction hybrid cladding (LIHC) as a result of liquid phase separation (LPS). The microstructure exhibited by large amounts of ferromagnetic (FM) Fe3Si particles dispersed within the ε-Cu matrix in the upper layer, and many ε-Cu particles embedded within the FM Fe3Si matrix in the lower layer. The microhardness values of the Fe3Si matrix lower layer (758HV0.2) and ε-Cu matrix upper layer (248HV0.2) were ∼7.3 and ∼2.4 times higher than that of pure copper by LIHC, respectively, indicating that the immiscible composite exhibited strongly inhomogeneous characteristics consistent with a “bilayer structure”. Moreover, the immiscible composite showed a high saturation magnetization of 96.2 emu/g and a low coercivity of 7.24 Oe due to the formation of FM Fe3Si with micro- and nanoscaled structures.

Phase separation and properties of Cu-Fe-Cr-Si-C immiscible nanocomposite by laser induction hybrid cladding

A Cu-Fe-Cr-Si-C immiscible nanocomposite has been produced via laser induction hybrid cladding (LIHC) as a result of liquid-liquid phase transformation. The nanocomposite has a bilayer structure composed of many nanoscaled ferromagnetic (FM) α-Fe(Si) particles (∼50 nm) embedded within the Cu-rich ε-Cu matrix in the upper layer, and large amounts of nanoscaled Cu-rich ε-Cu particles (∼30 nm) dispersed within FM α-Fe(Si) matrix in the lower layer. As a result, the nanocomposite exhibits an enhanced "bilayer-microhardness" and a comparative corrosion resistance to pure copper produced by LIHC. Interestingly, the nanocomposite also presents a relatively high saturated magnetization (∼84.6 emu/g), a low coercivity (∼0.65 Oe), and a sudden jump of magnetization at ∼310 K during heating.

Phase separated characteristics and soft magnetic properties of [Cu0.6(FeCrC)0.4]100−xSix immiscible composites by laser induction hybrid cladding

The effect of Si addition on phase separation and soft magnetic properties of [Cu0.6(FeCrC)0.4]100-xSix (x = 3 and 8) immiscible composites produced by laser induction hybrid cladding (LIHC) has been investigated. The duplex structure of immiscible composites was composed of many Fe-rich particles dispersed within Cu-rich upper layer and large amounts of Cu-rich particles embedded within Fe-rich lower layer. However, the increasing Si addition not only induced the precipitation of intermetallic compound Cu6.69Si within Cu-rich upper layer, but also increased the area of Fe-rich layer, the size of Fe- and Cu-rich particles, as well as the solubility of Si in Fe- and Cu-rich phases. Moreover, the microhardness of Fe- and Cu-rich layers was increased to 747.3HV0.2 and 302.6HV0.2 in the Cu55.2(FeCrC)36.8Si8 immiscible composite, respectively, which was ∼1.6 and ∼1.8 times higher than that in the Cu58.2(FeCrC)38.8Si3 immiscible composite, due to solid-solution strengthening and dispersion strengthening. Compared to the Cu58.2(FeCrC)38.8Si3 immiscible composite, the Cu55.2(FeCrC)36.8Si8 immiscible composite presented a saturated magnetization of 13.7 emu/g, relatively lower coercivity of 24.9 Oe and higher Curie temperature of larger than 400 K due to appearance of ferromagnetic α-Fe(Si) phase.

High-temperature slide wear of Ni-Cr-Si metal silicide based composite coatings on copper substrate by laser-induction hybrid cladding

Laser cladding is an effective way to improve wear resistance of copper alloys, however, low deposition rate is a main drawback that retards its industrial applications. Metal silicide based composite coatings were prepared on pure copper substrate by laser-induction hybrid cladding with a 5kW fiber laser efficiently, and the powder feeding rate can reach 88.7g/min. Cr13Ni5Si2, Cr3Ni5Si2 and Cu-based solid solution (Cuss) are main constituent phases in the composite coatings. Moreover, hardness of the different phases was evaluated by nanoindentation. Results indicated that the Cr13Ni5Si2 with high hardness (15.8GPa) is acted as strengthen phase in the composite coatings, while the Cr3Ni5Si2/Cuss with good toughness are acted as toughness phases. Synergistic effect of the strengthen phase and the toughness phases endows the composite coating with excellent wear resistance, and dry slide wear resistance of the composite coating at 600°C is 21.9 times higher than that of the stainless steel 1Cr18Ni9Ti.

Microstructure evolution of phase separated Fe-Cu-Cr-C composite coatings by laser induction hybrid cladding

To investigate the cooling rate on the microstructure evolution of phase separated Fe-Cu composite coatings by laser induction hybrid cladding (LIHC), the different laser scanning speed is adopted to estimate the temperature profiles and cooling rate of the molten pool. When the low laser scanning speed is adopted during LIHC, the Cu-rich spherical particles are embedded dispersedly in the Fe-rich interdendrites at the bottom of coating, while the nanostructured Fe-rich dendrites and the Fe-rich particles are distributed simultaneously in the Cu-rich matrix at the top of coatings. However, the increasing of laser scanning speed can decrease the temperature of the molten pool and increase the cooling rate of the molten pool. This in turn leads to an increase in dynamic supercooling and solute trapping of Cu in the enhanced Fe-rich dendritic refinement, but a decrease in size of Fe- and Cu-rich particles as well as a reduction in size of nanostructured Cu-rich grains inside the Fe-rich particles due to the secondary liquid phase separation.

Effect of substrate types on the microstructure and properties of Cu65Fe35 composite coatings by laser induction hybrid cladding

The Cu65Fe35 (wt.%) composite coatings with a liquid miscibility gap were produced on the different substrates by laser induction hybrid cladding (LIHC) to investigate the effect of substrate types on the microstructure and properties. The microstructure of composite coating on Fe-substrate is characterized by Cu-rich particles embedded in Fe-rich layer and Fe-rich particles dispersed in Cu-rich layer, resulting in Cup/Fe-Fep/Cu “duplex-layer structure”. When Cu-substrate is adopted, the interlayer is Fe-rich layer where Cu-rich particles are distributed, and is enveloped by the upper and lower Cu-rich layers where Fe-rich particles are embedded dispersedly, resulting in Fep/Cu-Cup/Fe-Fep/Cu “sandwich-layer structure”. Moreover, the composite coating on Fe-substrate presents the characteristic of “duplex-microhardness”, which is composed of Fe-rich layer with higher microhardness and Cu-rich layer with lower microhardness. The composite coating on Cu-substrate presents the characteristic of “sandwich-microhardness”, which is composed of Fe-rich interlayer with higher microhardness, lower and upper Cu-rich layer with lower microhardness. With increasing distance from the interface of coating/substrate, the microhardness of heat-affected-zone (HAZ) in Fe-substrate decreases, while that of HAZ in Cu-substrate decreases first and then increases. The electrochemical resistance of composite coating on Fe-substrate is higher than that of composite coating on Cu-substrate, Brass, and middle carbon steel (MCS).