Laser Cladding Coatings Research Articles

Wear Resistance of Fe-Based Amorphous Powder Deposited Coatings in Air, Water, and SBF Solution: Effect of Layer Number

Amorphous alloys have high strength and high hardness, showing their potential applications as tribological materials. In order to improve the wear resistance of 316L stainless steel (SS), Fe-based amorphous powder was deposited on 316L SS by laser cladding. Since the microstructure of the laser clad coating was sensitive to the dilution between coating and substrate, multilayer Fe-based metallic coatings were fabricated layer by layer. When the laser cladding layer number increased, the microstructure evolved from a complete crystalline phase to a mixed structure with amorphous phase and dendrite. Meanwhile, the amorphous content increased and the average microhardness was enhanced. Accordingly, the wear resistance was improved generally under all the sliding conditions, including in air, distilled water, and simulated body fluid (SBF) solution. For the lubricant effect of liquid, the coefficients of friction in distilled water and SBF solution are relatively lower than that in air. Compared with 316L SS, the volume loss rate of nine-layer coating decreased by two orders of magnitude in air and about 5.5 times in SBF solution. Except for one-layer coating, the predominant wear mechanism of the laser clad coatings in air is abrasive wear accompanied by oxidative wear. The wear mechanism in SBF solution is dominated by abrasive wear and corrosive wear. The superior hardness and good corrosion resistance are responsible for the outstanding wear resistance improvement. Therefore, the laser clad coating with Fe-based amorphous alloy has a potential application in the surface strengthening of mechanical parts or metallic implants.

Microstructure and Mechanical Properties of Multi-Phase Reinforced MoFeCrTiWNb2.5(Al2O3)x High-Entropy Alloy Laser Cladding Coatings

Microstructure and Mechanical Properties of Multi-Phase Reinforced MoFeCrTiWNb2.5(Al2O3)x High-Entropy Alloy Laser Cladding Coatings

Microstructural Properties and Wear Resistance of Fe-Cr-Co-Ni-Mo-Based High Entropy Alloy Coatings Deposited with Different Coating Techniques

Materials can be subjected to severe wear and corrosion due to high temperature, high pressure and mechanical loads when used in components for the production of geothermal power. In an effort to increase the lifetime of these components and thus decrease cost due to maintenance High-Entropy Alloy Coatings (HEACs) were developed with different coating techniques for anti-wear properties. The microstructure, mechanical and tribological properties of CoCrFeNiMox (at% x = 20, 27) HEACs deposited by three different technologies—high-velocity oxygen fuel (HVOF), laser cladding (LC) and electro-spark deposition (ESD)—are presented in this study. The relationship between surface morphology and microstructural properties of the as-deposited coatings and their friction and wear behavior is assessed to evaluate their candidacy as coatings for the geothermal environment. The wear rates were lower for the HVOF coatings compared to LC and ESD-produced coatings. Similarly, a higher hardness (445 ± 51 HV) was observed for the HVOF HEACs. The mixed FCC, BCC structure and the extent of σ + µ nano precipitates are considered responsible for the increased hardness and improved tribological performance of the HEACs. The findings from the study are valuable for the development of wear-resistant HEAC for geothermal energy industry applications where high wear is encountered.

Investigation into the Corrosion Wear Resistance of CoCrFeNiAlx Laser-Clad Coatings Mixed with the Substrate

CoCrFeNiAlx (x = 0 and 1.0) high-entropy alloy coatings were synthesized on Ti6Al4V via laser cladding to improve their corrosion and wear resistance under corrosive conditions. Results indicated that the coating (CoCrFeNi) was largely composed of irregular primary α(Ti) and honeycomb-like eutectics of α(Ti) + Ti2Ni as the matrix, with TiC dendrites as the reinforcement. When Al was introduced into the cladding material, irregular α(Ti) grains were transformed into equiaxed grains, besides which the area fraction in eutectics was considerably reduced, and TiC dendrites were also transformed into spherical particles. Compared with the coating without Al, the introduction of Al contributed to the improvement in corrosion resistance because corrosion potential was enhanced from −0.524 V to −0.393 V, whereas corrosion current density and steady current density were reduced from 2.249 × 10−7 A·cm−2 and 1.021 × 10−6 A·cm−2 to 1.260 × 10−7 A·cm−2 and 2.506 × 10−7 A·cm−2, respectively. The substrate was still at the break-in stage during a long-term sliding of 10 h because its wear rate exhibited an approximately linear reduction tendency (2.09 × 10−3 mm3·N−1·m−1 for 2 h and 7.44 × 10−4 mm3·N−1·m−1 for 10 h). With respect to the coatings, they transitioned from the break-in stage into the stable wear stage when the sliding duration exceeded 4 h, during which a comparatively stable wear rate of 2.88 × 10−4 mm3·N−1·m−1 was obtained. The wear mechanism of the substrate was identified as slight microcutting and serious oxidation for the long-term sliding of 10 h. It changed into a combination of slight microcutting, serious oxidation, and moderate brittle debonding for the coatings. Generally speaking, the introduction of Al can refine the microstructure and improve the microstructural uniformity. Moreover, the passive film can be formed more rapidly on the coating surface and presents higher stability when introducing Al. Finally, the introduction of Al also promotes the coating to enter into the stable wear stage more rapidly and causes the decrease in friction coefficient and wear rate.

Effect of Cr Content on Corrosion Resistance of Ni-xCr-Mo Laser-Cladding Coatings under H2S-Induced High-Temperature Corrosion Atmosphere.

Ni–xCr–Mo laser-cladding coatings with varying Cr content of 10, 15, 20, 25, and 30 wt.% were fabricated using a self-assembled coaxial laser-cladding device. The H2S-induced high-temperature corrosion tests under reductive atmosphere were conducted at 500, 550, and 600 °C. Subsequently, the influence of Cr content on the microstructural evolution and corrosion resistance of the Ni–xCr–Mo coatings was investigated. The experimental results revealed that 30 wt.% Cr is the limited maximum content that forms the suitable morphology of coatings without large prominent pores and cracks during the fabrication process, and 15 wt.% Cr corresponds to the critical minimum content for excellent corrosion resistance, as implied from the variation tendency of the corrosion weight-gain curves. Moreover, a two-layer structure of the corrosion scales was observed in the Ni–xCr–Mo laser-cladding coatings, which was primarily caused by the selective corrosion between the Ni and S and Cr/Mo and O.

Development of a novel method for measuring the interfacial creep strength of laser cladding coatings

In this study, the effect of IN713 coating applied by the laser cladding method on the creep behavior of GTD-111 superalloy by a small punch creep test was investigated. For this purpose, the creep behavior of the specimens in different parts in three conditions of casting, solution heat treatment, and aging was compared. The results showed that the specimen selected from the coating-substrate interface shows the highest creep resistance among other parts. This is attributed to the obstacle to the movement of dislocations by the coating-substrate interface from the substrate to coating. Also, in the aged specimens, due to the increase in γ′ phase volume fraction, the highest creep resistance was obtained. The heat-affected zone (HAZ) of the casting specimen had the lowest creep position due to the formation of partial liquation and cracking by γ-γ′ eutectic, M5B3 boride, Ni-Zr interface, and MC carbide. This problem was solved by performing solution heat treatment before coating and aging after coating.

Nondestructive measurement of the grain size of laser cladding coatings using a laser ultrasonic method.

Due to the processing characteristics of laser cladding, the beads and joints of the laser cladding coatings have different grain sizes. We used the laser ultrasonic (LU) method to measure the distribution of the grain sizes of laser cladding coatings nondestructively. The surface acoustic wave amplitude was influenced by the grain size; hence, the amplitude varied for beads and joints because of their different attenuations. The spatial resolution of LU is higher than that of the traditional ultrasonic testing method, leading to a fringe distribution of the C-scan results in the scanning area. The LU results were verified through metallographic experiments. It was concluded that the LU method can be used to determine the grain sizes of coatings.

Microstructure evolution and wear resistance of laser cladded 316L stainless steel reinforced with in-situ VC-Cr7C3

Laser cladding (LC) has been applied to enhance the wear resistance of 316L coatings by depositing in-situ VC-Cr7C3 metal matrix composites (MMCs) coating on structural steel substrate using pre-mixed powder consisting of vanadium, carbon, and 316L stainless steel. The effects of different process parameters, varied V and C contents on the phase constituents, microstructure, and the mechanical properties of 316L LC coatings were investigated systematically. The related microstructure evolution and the mechanical properties were comprehensively studied. The results indicated that under the selected laser irradiance of 80 W/mm2, scanning rate of 4 mm/s, and powder feeding rate of 10 g/min, by increasing V and C content from 0 wt % to 14 wt %, VC, Cr7C3, and Cr23C6 would be progressively precipitated at grain boundaries, and the austenite grains tended to be refined. Consequently, the microhardness of reinforced 316L coatings significantly increased from 207 HV1 to 467.8 HV1. Wear tests showed that the wear resistance improved some 8 times compared to the pure 316L layer under the dry sliding condition, and the dominating wear mechanism for the cladding transferred from adhesive wear to abrasive wear. Further microstructure characterization revealed that besides precipitation strengthening and fine-grain strengthening, the strengthening effect was also originated from the interfacial structure between the precipitated carbides, including a coherent interface for γ/Cr7C3, semi-coherent interfaces for γ/VC, and VC/Cr7C3. Based on the results of thermodynamic calculation and Fe-Cr-C ternary phase diagram, the spherical VC acted as the nucleation sites for the dispersed carbide reinforcement and the austenite grains, and the inhibition against austenite matrix growth by ceramic precipitations dispersedly distributed along the grain boundaries.

Microstructure and elevated temperature wear behavior of laser-cladded AlCrFeMnNi high-entropy alloy coating

The AlCrFeMnNi high-entropy alloy (HEA) coatings were deposited on 316L stainless steel through laser cladding technology that employs pre-alloyed HEA powders. The microstructure, phase composition and hardness of the laser-cladded coatings prepared at different laser scanning speeds were investigated. The wear behavior and properties of the HEA coatings at different temperatures (from room temperature to 600 °C) was comprehensively evaluated using a pin-on-disc test. It was demonstrated that the laser-cladded AlCrFeMnNi HEA coatings exhibited dense and uniform microstructures consisting of a single BCC solid solution phase. A columnar-to-equiaxed transition structure feature was observed in the molten pool of the laser-cladded coating. The coatings possessed better high-temperature wear performance due to the protective effect of oxide films on the wear track. The coating at 400 °C exhibited the best wear resistance, which had the lowest friction coefficient and wear rate of 0.48 and 1.246 × 10−4 mm3/N · m, respectively. At room temperature, the main wear mechanism of the coating was abrasive wear. However, the predominant wear mechanism at high temperatures was oxidation and adhesive wear.

2Pa2-2 Detection of interface defects in laser-cladding coatings using laser ultrasonic method

2Pa2-2 Detection of interface defects in laser-cladding coatings using laser ultrasonic method

Preparation, Microstructure Evolution and Performance of Laser-Cladded Titanium Alloy Coating on Mild Steel

Preparation, Microstructure Evolution and Performance of Laser-Cladded Titanium Alloy Coating on Mild Steel

Preparation, Microstructure Evolution and Performance of Laser-Cladded Titanium Alloy Coating on Mild Steel

Preparation, Microstructure Evolution and Performance of Laser-Cladded Titanium Alloy Coating on Mild Steel

Characterization of Elastic Modulus of Laser Cladding Coatings Using Laser Ultrasonic Method

Characterization of Elastic Modulus of Laser Cladding Coatings Using Laser Ultrasonic Method

Achieving High Surface Integrity of Fe-Based Laser Cladding Coating by Optimized Temperature Field-Assisted Ultrasonic Burnishing

Achieving High Surface Integrity of Fe-Based Laser Cladding Coating by Optimized Temperature Field-Assisted Ultrasonic Burnishing

Controlling the Microstructure and Properties of Yf3 Modification Niti-Si Laser Cladding Coatings by Heat Treatment and Cryogenic Treatment

Controlling the Microstructure and Properties of Yf3 Modification Niti-Si Laser Cladding Coatings by Heat Treatment and Cryogenic Treatment

Effect of Heat and Cryogenic Treatments on the Microstructure and Properties of Yf3 Modified Niti-Si Laser Cladding Coatings

Effect of Heat and Cryogenic Treatments on the Microstructure and Properties of Yf3 Modified Niti-Si Laser Cladding Coatings

Microstructures and high-temperature oxidation behavior of laser cladded NiCoCrAlYSi coating on Inconel 625 Ni-based superalloy modified via high current pulsed Electron beam

NiCoCrAlYSi coatings were prepared on the surface of nickel-based high-temperature alloys (Inconel 625) by laser cladding (LC) technique, and then the surface was modified by high current pulsed electron beam (HCPEB). The microstructural results indicate that metallurgical defects on the original surface, including micropores and elemental segregations were eliminated, and a remelted layer consisting of high density of cross slips and nanostructures was obtained. High-temperature oxidation resistance at 900 °C, 1000 °C and 1100 °C of the original coatings was investigated. When oxidized at 900 °C for 100 h, the original coating followed the linear growth law, and the TGO was mainly consisted of Al 2 O 3 . When oxidized at 1000 °C and 1100 °C for 100 h, the original coating followed the parabola law, and the TGO existed in a double-layer structure. After HCPEB irradiation, a rather stable, continuous, and slow-growing α-Al 2 O 3 was formed on the surface after oxidation for 100 h at 1100 °C. The kinetic curves show that the growth rate of the TGO of the irradiated coatings was reduced by 43.9%, and the thickness was effectively decreased compared with the original sample. Thus, HCPEB technique is proved to be an effective method to improve the service life of laser cladding coatings. • Microstructures and oxidation behavior of NiCoCrAlYSi laser cladding coating was investigated. • Cladding coatings presented different oxidation rate and growth behavior at different temperatures. • HCPEB technique was used to further improve the microstructures and properties of cladding coating. • Restructured surface promoted the formation of a protective α-Al 2 O 3 layer at 1100 °C. • HCPEB technology is an effective way to improve the high-temperature service life of cladding coatings.

Quality evaluation of multi-path laser cladding coatings based on integrated fuzzy comprehensive evaluation and improved analytical hierarchy process method

Laser cladding processes have a wide range of applications for enhancement and surface modification of material characteristics. However, due to their coating formation's complexity, there is no practical method to value the cladding's quality. In this paper, a fuzzy comprehensive evaluation (FCE) model and the evaluation process are proposed. The quality evaluation index framework is demonstrated from the macroscopic profile, microstructure, and mechanical properties, and the assessment indexes are weighted by an improved analytic hierarchy process (IAHP) approach. Each indicator quantifies at four degrees. A stepwise affiliation function is used to calculate each indicator's affiliation at different degrees, then used to assess the project's quality level. This approach can help to improve surface quality analysis' reliability and optimize processing parameters.

Corrosion Behavior of FeNiCrMoSiC Laser Cladding Coatings with Different Addition of Ni Content in Acidic Environment

Three FeNiCrMoSiC laser cladding coatings with different Ni content were deposited on AISI 4130 substrate. The electrochemical corrosion behavior of three FeNiCrMoSiC coatings in 0.5 mol/L HCl solution was investigated by the polarization curve and electrochemical impedance spectroscopy measurement. X-ray photoelectron spectroscopy and Mott-Schottky tests were employed to evaluate the passive film on the coating surface to investigate the passivation stability mechanism of the coating in hydrochloric acid. Potentiodynamic polarization results show that the FeNiCrMoSiC coatings shown superior corrosion resistance than the AISI 4130 substrate, demonstrated by lower corrosion current density and higher corrosion potential. With the increase of Ni concentration, the content of austenite γ-Fe phase increased, whilst the volume of ferrite α-Fe phase decreased, and the corrosion resistance of FeNiCrMoSiC coatings also increased. The main reason for the excellent corrosion resistance of the coating is the barrier effect of bilayer oxide passive film, which is difficult to dissolve in acid and can effectively slow down the penetration of corrosive ions in hydrochloric acid solution on the coating surface.

Development of a novel method for measuring the interfacial bonding strength of laser cladding coatings

Interface bonding strength is a crucial factor that determines the final mechanical properties and performance of laser cladding coatings. Due to the metallurgical bonding caused by laser cladding, the traditional method of measuring normal interface bonding strength is difficult to use. The present paper proposes a self-designed T-shaped sample and related fixtures to characterize the interface bonding strength. Tensile tests are performed on T-shaped specimens with different cross-sectional areas, and one of the shapes is used for subsequent testing. The fracture morphology of the T-shape samples presented obvious dimples and cleavage steps at the fracture, indicating that the fracture mechanism is hybrid fracture. When the laser power is 2200 W, the T-shaped sample has a higher interface bonding strength of 637 MPa. The effectiveness and repeatability of the method are proved by comparative experiments. This study provides new insights into the better evaluation of laser cladding interface bonding strength in engineering applications.