Cladding Coatings Research Articles

Corrosion Behavior of Fe-Based Laser Cladding Coating in Hydrochloric Acid Solutions

Corrosion Behavior of Fe-Based Laser Cladding Coating in Hydrochloric Acid Solutions

Microstructure and dry-sliding wear properties of TiC/CaF2/γ-Ni self-lubricating wear-resistant composite coating produced by co-axial powder feeding plasma transferred arc (PTA) cladding process

For improving the surface tribological properties of AISI 304, co-axial powder feeding PTA cladding process was adopted to produce the TiC/CaF2/γ-Ni self-lubricating wear-resistant composite coating on AISI 304 substrate using powders blend of Ni, Ti, Ni-P encapsulated CaF2 and Ni-P encapsulated graphite as raw material. The TiC/γ-Ni wear-resistant composite coating as reference was also fabricated on AISI 304 substrate by co-axial powder feeding PTA cladding process using powders blend of Ni, Ti and Ni-P encapsulated graphite as raw material. OM, SEM, XRD and EDS were employed to analyze the microstructure of the PTA cladding coatings. Microhardness distribution along the depth direction of the PTA cladding coatings was measured. Dry-sliding wear resistance of the PTA cladding coatings were evaluated. Test results show that the PTA clad TiC/CaF2/γ-Ni composite coating with an average thickness of 3.2 mm as well as fine and dense microstructure was successfully produced by co-axial powder feeding PTA cladding process. The PTA clad TiC/CaF2/γ-Ni composite coating exhibits high hardness and excellent self-lubricating wear-resistant properties compared with AISI 304 reference specimen. Benefiting from the formation of low shear strength transferred layers which mainly consists of CaF2 solid-lubricating phase, the PTA clad TiC/CaF2/γ-Ni coating presents higher wear resistance and lower friction coefficient compared with the PTA clad TiC/γ-Ni coating, although its hardness is lower than that of the PTA clad TiC/γ-Ni coating.

In situ synthesis of TiC-TiN-reinforced Fe-base plasma cladding coatings

ABSTRACTUsing titanium, boron carbide and iron-based alloy powders as reactive sources, an Fe-based cladding coating reinforced by in situ synthesised TiC-TiN particles was fabricated using the plasma cladding method. The effects of Ti and B4C content on the phase composition, microstructure, microhardness, wear resistance and corrosion resistance of the coating were studied. The cladding coatings were composed of α-Fe, Cr, Fe3C, TiC, TiN, Fe23B6 and Fe23(C,B)6. The relative content of TiC, TiN, Fe23B6, and Fe23(C,B)6 in the cladding layer increased with an increase in Ti and B4C contents. The hardness, wear resistance and corrosion resistance of the cladding coating increased with an increase in Ti and B4C content. The results indicated that the composite coatings exhibited excellent wear resistance and corrosion resistance.

Progress and Challenges of Ultrasonic Testing for Stress in Remanufacturing Laser Cladding Coating.

Stress in laser cladding coating is an important factor affecting the safe operation of remanufacturing components. Ultrasonic testing has become a popular approach in the nondestructive evaluation of stress, because it has the advantages of safety, nondestructiveness, and online detection. This paper provides a review of ultrasonic testing for stress in remanufacturing laser cladding coating. It summarizes the recent research outcomes on ultrasonic testing for stress, and analyzes the mechanism of ultrasonic testing for stress. Remanufacturing laser cladding coating shows typical anisotropic behaviors. The ultrasonic testing signal in laser cladding coating is influenced by many complex factors, such as microstructure, defect, temperature, and surface roughness, among others. At present, ultrasonic testing for stress in laser cladding coating can only be done roughly. This paper discusses the active mechanism of micro/macro factors in the reliability of stress measurement, as well as the impact of stress measurement on the quality and safety of remanufacturing components. Based on the discussion, this paper proposes strategies to nondestructively, rapidly, and accurately measure stress in remanufacturing laser cladding coating.

Effect of molybdenum on the high-temperature properties of TiC-TiB2 reinforced Fe-based composite laser cladding coatings

Fe-Ti-B-Cr-Mo-C composite coatings with different molybdenum (Mo) content were in-situ fabricated on a 5CrNiMo die steel substrate by laser cladding. Effects of Mo on the microstructure and high -temperature properties of coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), high-temperature oxidation and high-temperature wear resistance test. Results showed that block-like or cuboidal TiB2 and Mo2B, as well as flower-like (Ti,Mo)C reinforced particles have been formed in the coatings. Amounts of martensite in the coating increased with the increasing of Mo. However, cracks are found in the coating while the addition of FeMo70 exceeded 9 wt%. Mo improved the high-temperature oxidation resistance and reduced oxidation rate. Besides, the coatings processed the better high-temperature wear resistance with 9 wt% FeMo70.

Microstructure and Formation Mechanism of in-Situ TiN-TiB2 /Ni Coating by Argon Arc Cladding

Abstract An in situ synthesis method was developed to produce a Ni alloy composite coating reinforced by in situ reacted TiN and TiB2 particles using argon arc cladding (AAC) with different molar ratios of BN/Ti on a 35CrMnSi steel substrate. The microstructures of the clad coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results show that the phases of the coating are TiN, TiB2, TiB, Cr23C6 and γ-Ni. As the BN/Ti ratio increases, the needle-like TiB phase almost disappears and the number of rod-like TiB2 particles increases. Their shape become smaller. The computed results show that the nucleation driving force of the major reinforcing phases from low to high is TiN-TiB2-TiB at different test temperatures. Moreover, the growth mechanism of the phases was discussed in the Ti-BN-Ni system. When the BN/Ti molar ratio is 0.67 the clad coating shows the highest average micro-hardness and excellent wear resistance at room temperature under normal atmosphere conditions.

Effect of Ultra-fine WC Particles on Microstructural Evolution and Wear Behavior of Ni-Based Nano-CeO2 Coatings Produced by Laser

The wear behavior and microstructure of CO 2 laser cladded Ni-based alloy coatings with 1 wt% nano-CeO 2 and 20 wt% WC addition (CeO 2 /Ni) was compared with Ni-based coatings with 1 wt% nano-CeO 2 addition (WC-CeO 2 /Ni). Both coatings were cladded on 30CrMnSiNi2A steel with good metallurgical bounding to substrate. The influence of ultra-fine carbide WC on the microstructure of WC-CeO 2 /Ni alloy composite coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) and electron probe micro analysis (EPMA). WC addition increased M 23 C 6 content, but decreased the M 7 C 3 . The comparison of comprehensive mechanical properties between coatings with and without fine WC particles was conducted on Vickers hardness and wear-resistance test system. Results indicate that the performance of WC-CeO 2 /Ni is better than that of CeO 2 /Ni metal matrix composition (MMC). Few hot cracks appeared in Ni-based WC-CeO 2 MMC production, which were investigated by SEM and EDS. The crack mechanism can be claimed as Fe dilution and coefficient of thermal expansion for WC-CeO 2 /Ni MMC differed from that of base material 30CrMnSiNi2A steel.

Effect of laser scanning speed on surface properties of Ti-Si laser clad intermetallic coatings fabricated on Ti-6Al-4V alloy

A binary Ti-Si (1 : 1) alloy coating was fabricated on Ti-6Al-4V alloy using laser cladding technique where Neodymium yttrium aluminium garnet laser was utilised. Micro-atomised powders of Ti and Si were used for deposition of multi-track clad coatings utilising power of 1.5 kW and a varied speed of 1.2 m/min, 1.6 m/min and 2.0 m/min. Scanning electron microscope coupled with energy dispersive spectrometer was used for microstructural characterisation and elemental analysis while a digital light microscope was used for optical imaging and coating thickness measurements. Phase identification was conducted using X-ray diffraction analyser and transverse microhardness evaluated at 100 gf for 10 s dwell time was achieved with the use of a Vickers hardness machine. The laser fabricated coatings were found to exhibit a decrease in grain size with an increase in the laser scanning speed. The microstructure of the coatings ranged from irregular refined grains, faceted grains and lamellar eutectic network of TiSS + Ti5Si3. The hardness of the coatings exhibited Ti, Si, TiS2 and Ti5Si3 phases averaged a 247.4% increase with maximum hardness recorded at 1.2 m/min scanning speed.

Microstructure and properties of Ti/TiBCN coating on 7075 aluminum alloy by laser cladding

Ti/TiBCN coatings were fabricated on the 7075 aluminum alloy by laser cladding. The influence of TiBCN content on microstructure, micro-hardness, electrochemical corrosion and wear resistance of the cladding coatings were studied by SEM, XRD, Vickers micro-hardness tester, a typical three-electrode electrochemical workstation and straight-line-reciprocating dry sliding wear tester, respectively. The results showed that, when TiBCN content was 15wt%, the microstructure of coating zone mainly composed of equiaxed grains and white lath-like crystals and that of transition zone mainly consisted of the elongated dendrite crystals and white small particles. Furthermore, the average hardness of the Ti/TiBCN cladding coating is 750HV0.2, which was about 5 times higher than that of the substrate (~127HV0.2), and the corrosion potential (Ecorr) reached −1.271V and the corrosion current density (Icorr) was 3.155e−005A/cm2, which was one magnitude low than that of the substrate (2.269e−004A/cm2). The narrow and shallow plowing grooves uniformly distributed on the worn surface and have less wear damage and the mass loss of the cladding coating was only 2.4mg in 20min.

Initial experimental evaluation of crud-resistant materials for light water reactors

The buildup of fouling deposits on nuclear fuel rods, known as crud, continues to challenge the worldwide fleet of light water reactors (LWRs). Crud causes serious operational problems for LWRs, including axial power shifts, accelerated fuel clad corrosion, increased primary circuit radiation dose rates, and in some instances has led directly to fuel failure. Numerous studies continue to attempt to model and predict the effects of crud, but each assumes that it will always be present. In this study, we report on the development of crud-resistant materials as fuel cladding coatings, to reduce or eliminate these problems altogether. Integrated loop testing experiments at flowing LWR conditions show significantly reduced crud adhesion and surface crud coverage, respectively, for TiC and ZrN coatings compared to ZrO2. The loop testing results roughly agree with the London dispersion component of van der Waals force predictions, suggesting that they contribute most significantly to the adhesion of crud to fuel cladding in out-of-pile conditions. These results motivate a new look at ways of reducing crud, thus avoiding many expensive LWR operational issues.

Effect of Mo on Microstructures and Wear Properties of In Situ Synthesized Ti(C,N)/Ni-Based Composite Coatings by Laser Cladding.

Using Ni60 alloy, C, TiN and Mo mixed powders as the precursor materials, in situ synthesized Ti(C,N) particles reinforcing Ni-based composite coatings are produced on Ti6Al4V alloys by laser cladding. Phase constituents, microstructures and wear properties of the composite coatings with 0 wt % Mo, 4 wt % Mo and 8 wt % Mo additions are studied comparatively. Results indicate that Ti(C,N) is formed by the in situ metallurgical reaction, the (Ti,Mo)(C,N) rim phase surrounding the Ti(C,N) ceramic particle is synthesized with the addition of Mo, and the increase of Mo content is beneficial to improve the wear properties of the cladding coatings. Because of the effect of Mo, the grains are remarkably refined and a unique core-rim structure that is uniformly dispersed in the matrix appears; meanwhile, the composite coatings with Mo addition exhibit high hardness and excellent wear resistance due to the comprehensive action of dispersion strengthening, fine grain strengthening and solid solution strengthening.

Effect of feed rate on laser surface cladding of cold rolled carbon steel

Oil and gas industries require much equipment and tools having extra ordinary hardness, strength, wear and chemical properties. They have been established well that the important manufacturing processes to achieve these properties are laser cladding of special alloys on cheap substrates such as carbon steels. In order to achieve the optimum properties for these industries, controllable dilution between substrate and clad coating should obtained. In this study, the performance of laser cladding is found to be controlled by two important outputs geometry dimensions and microstructure. The geometry dimensions include many features of clad width, clad height, cont act angle, depth of penetration and dilution area. In order to determine the quality of clad coatings, these features were correlated with laser processing parameters such as specific energy. An experimental study has been concentrated on determine the all dimensions and dilution area on cladding Ni- 5 wt% Al mixed powder on a cold rolled low carbon steel. Wide ranges of traverse speeds in the range of 1.5 to 12.5 mm/s were used to produce clad coatings with different dilutions from the substrate. The laser power, laser beam diameter and powder feed rate employed were 1.8 kW, 2.5 mm and 10 g/min respectively; the specific energies used were 58 to 480 J/mm2. Many single or combined features were developed and their values were determined for cladding tracks having different dilutions. It was postulated that the successful cladding process could be described by new developing terms such as effective clad thickness, effective clad dimensions, dilution aspect ratio and effective specific energy. The data obtained could be used effectively to distinguish between cladding and highly alloyed tracks as a function of specific energy and geometry dimensions of the deposit coatings.

An assessment of microstructure and properties of laser clad coatings of ultrafine eutectic β Ti-Fe-Nb-Sn composite for implants

High mechanical strength (1800–2500MPa), elastic modulus (50–110GPa) close to that of human bone and good corrosion resistance are some characteristics of ultrafine eutectic Ti-based nanocomposite alloys. This is explained due to a combination of soft β-Ti (bcc) matrix and hard/refined TiFe and/or Ti3Sn intermetallic particles. The present study focuses on the production and characterization of Ti-Fe-Nb-Sn eutectic alloys using biocompatible β-stabilizer elements, such as Nb, Fe and Sn. Different fabrication techniques based on rapid solidification may be highlighted considering the application of these alloys as implant materials. In the present investigation, the processing routes comprise single tracks and coatings (overlapped tracks) by laser melting of pre-alloyed powders of the Ti66Fe20Nb8Sn6 alloy deposited into a Ti substrate. To select this composition (i.e., the Ti66Fe20Nb8Sn6 alloy), three Ti-Fe-Nb based chemistries (Ti63Fe23Nb8Sn6, Ti60Fe23Nb8Sn9 and Ti66Fe20Nb8Sn6) were originally generated under bulk conditions by using a suction casting apparatus. These alloys were further evaluated. All samples were analyzed by metallography, X-ray diffraction (XRD), scanning electron microscopy (SEM-EBSD and SEM-EDS), microhardness, nanohardness and elastic modulus. The results showed that the proportions of the formed TiFe and Ti3Sn intermetallic particles dispersed within the soft β-Ti matrix play a fundamental role on the final properties. Lower elastic modulus (E ~72GPa) is associated with the Ti66Fe20Nb8Sn6 bulk alloy. The laser clad coatings showed a broad range of nanohardness (4.8–8.0GPa) and elastic modulus (98–150GPa) depending on the related laser power and scanning speeds.

Effect of Isothermal Temperature on Growth Behavior of Nanostructured Bainite in Laser Cladded Coatings.

The growth and propagation behavior of austenite-to-bainite isothermal transformation in laser-cladded, Si-rich, and Fe-based coatings is investigated. The crystallographic features, orientation relationship at different isothermal temperatures, and the morphology of the nanostructured bainite are determined. The Nishiyama-Wassermann type orientation relationship is observed at a high temperature and at a low temperature, and mixed Nishiyama-Wassermann and Kurdjumov-Sach mechanisms are seen. The growth direction is investigated by the partial dislocation theory and an extrapolated model based on the repeated formation of lenticular-shaped subunits and pile-up along the close-packed directions of the close-packed planes. The variants of the bainite growth directions would be more selective at the high transformation temperature.

A study on the influence of laser power on microstructural evolution and tribological functionality of metallic coatings deposited on Ti-6Al-4V alloy

Metallic Ti–Co binary coatings were fabricated on titanium alloy (Ti–6Al–4V) substrate by laser surface cladding technique using a continuous wave RofinSinar 4 kW Nd: YAG laser. The influence of laser power on microstructure, hardness and tribological performance of Ti–Co laser clad coatings on titanium alloy (Ti–6Al–4V) was examined. Laser powers of 750 and 900 W were varied with constant scan speed of 1.2 m/min. A beam size of 3 mm and argon shield gas flow rate of 1.2 L/min were set as the operating laser parameters. Phase identification and morphological studies of the coatings were carried out using X-ray diffractometry (XRD) and scanning electron microscopy (SEM), respectively. Based on the results of laser process optimisation, it was observed that both laser powers produced clad coatings with good metallurgical bond with no cracks or pores in the coatings. With respect to the substrate (Ti–6Al–4V), the microstructure, hardness and friction/wear behaviour of Ti–Co coatings on Ti–6Al–4V substrate were enhanced obviously.

Microstructure and wear resistance of laser cladding particulate reinforced Fe-based composite coating on railway steel

It has been proved that the laser cladding particulate reinforced metal-based composite coating is of great benefit to industrial applications, owing to its superior properties such as wear resistance, corrosion resistance, and metallurgical bond with a base metal. It is also well-known that the railway switch can easily get damaged due to the abominable conditions of high speed and heavy haul in the rail-wheel mechanical system, and it can cause quite huge loss every year. So, it is of great significance to increase the wear resistance of railway switch steel. In this study, particulate reinforced Fe-based composite coatings were produced on the high carbon manganese rail steel (U71Mn) by laser cladding. The coatings' properties, such as microstructure, microhardness, and wear resistance, were investigated. The wear scar appearance was also detected using a white light interferometer. The results reveal that the composite coatings with good formation and a typical in situ particulate reinforced microstructure can be obtained in proper processing ways. The microhardness of laser cladding coatings reaches HV 750 to HV 800, while the average microhardness of railway steel without laser treatment is HV 390. Furthermore, the properties of wear resistance of the laser cladding coatings have increased by nearly eight times when compared to the untreated railway steel specimen. The adhesion strength of the coatings to the substrate reaches 88% of the shearing strength of the railway steel.

Influence of large particle size – up to 1.2 mm – and morphology on wear resistance in NiCrBSi/WC laser cladded composite coatings

This paper aims at studying the influence of the reinforcement particle size and morphology on the wear resistance properties of NiCrBSi-based composites. Numerous papers have already been written on this subject but almost all of them studied the “conventional” particle size for laser cladding (i.e. between 20 and 200μm). The objective of this study is to see the influence of coarser reinforcement particles, up to 1.2mm, and the influence of the morphology (spherical and random shaped) on the coatings erosive and sliding wear resistance. Laser clad coatings were deposited on low carbon steel substrate S235JR with various amounts of WC/W2C particles up to 50vol.%. The coatings were processed by using a 3.8kW High Power Diode Laser (HPDL). Spherical tungsten carbide particles from 40μm up to 1200μm were used in this study as well as random shaped particles from 40μm to 400μm. To assess the influence of the reinforcement particle properties on wear properties, wheel tests and pin-on-disk tests were performed on each composition. From this study, it can be concluded that there is an obvious advantage in using larger particles (750–1200μm) in harsh conditions while smaller particles (40–160μm) improve the resistance in sliding conditions. The effect of morphology has not been proved significant.

Comparative Studies of Electrochemical and Mechanical Properties of Nickel Electrodeposited and Laser Fabricated Coatings on Steel

Choosing the right surface coating/modification technique is a challenging aspect of material design in recent years with respect to emerging and developing surface engineering technologies. Ni coatings were fabricated on mild steel (MS) samples using electrodeposition and laser cladding techniques respectively. Optical microscopy (OM), X-ray diffractometer (XRD), and scanning electron microscopy equipped with electron dispersive spectroscopy (SEM/EDS) were used to study the morphology, elemental composition, and phase evolution of coatings. Corrosion resistance and wear behaviour were investigated using electro Potentiostat and sliding ball wear tester, respectively. Laser clad Ni coating exhibited high wear resistance with high coefficient of friction, plastic deformation, and cracks on the surface, while Ni electrodeposited coatings had low wear resistance, low coefficient of friction, and eroded materials on the surface. Protective intermetallic oxide phases evolved on both the electrodeposited and the laser cladded coatings. Greater corrosion resistance in 3.65% NaCl solution was achieved through electrodeposition than through laser cladding of Ni on mild steel.

Effects of La2O3 on the microstructure and property of laser cladding Ni-based ceramic coating

Nickel based composite coatings with La2O3 addition were fabricated on medium carbon steel by laser cladding processing. The microstructure, phase composition, microhardness and corrosion resistance of the laser cladding coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), hardness tester and electrochemical workstation. The results show that the herringbone cracks generated in the deposited Ni-based ceramic coatings and the fracture mechanism exhibits quasi-cleavage fracture, while many tearing ridges and micro plastic deformations are present. A crack-free Ni-based composite ceramic coating is prepared with 0.6wt% La2O3 addition, and refined dendritic microstructures are formed with higher microhardness (659HV0.2). However, the introduction of La2O3 addition has little effect on the phase composition of the Ni-based ceramic coating, composed of γ-(Fe, Ni) solid solution, CrB, Cr23C6, Cr7C3 and WC. In addition, the Ecorr values of two kinds of laser cladding Ni-based coatings are all more positive than that of the as-received medium carbon steel, while the Ecorr value of Ni-based cladding ceramic coating with 0.6wt% La2O3 addition is more positive than that of Ni-based coating. Compared with Ni-based cladding coating, addition of 0.6wt% La2O3 leads to lower corrosion current density, which indicates the improved corrosion resistance.

Microstructure and sliding wear properties of HVOF sprayed, laser remelted and laser clad Stellite 6 coatings

The microstructure and sliding wear properties of Co-Cr-W alloy (Stellite 6) coatings were studied in the dependence on the deposition technology. The HVOF as-sprayed, laser remelted HVOF sprayed and laser clad coatings were evaluated by SEM, XRD and ASTM G-133 reciprocating sliding wear test. In dependence on used deposition technology, the microstructure of coating varied namely in terms of grain size and phase composition. The XRD analyses in the wear track revealed that the strain-induced fcc-to-hcp transformation is taking part during wear of laser remelted HVOF sprayed coatings. The difference of the phase composition, grain size and strain-induced fcc-to-hcp transformation was shown to be responsible for differences in the sliding wear behaviour.