Papers by Keyword: Laser Cladding

Abstract: The current research aimed to study microstructure evolution and wear resistance properties of coating layers on R900A rail steel. Powdery type laser cladding was carried out employing a three-jet coaxial laser nozzle by using the 3650 (Chromium-Nickel steel) powder. The key laser cladding parameters included a laser power of 1 - 1.5 kW, a scanning speed of 5 - 15 mm/s, and a powder feed rate of 10 – 20 g/min. After laser cladding completion, the coated specimens were carried out into the pin-on-disc tribometer for abrasive wear resistance evaluation compared to the reference rail material. The specimens were weighed before and after the wear test by an electronic balance with 0.0001g resolution. The hardness test and microstructure evolution were performed on the cross-sectional area of the specimen. After the wear test, the worn surface profile and wear morphology of the tested specimen were evaluated to determine the wear mechanism and severity. The hardness test shows that the 3650 had a higher hardness than the conventional rail steel. The microstructure of coating surfaces was composed of various carbide compounds such as Cr₂₃C₆ and Cr₇C₃, which are distributed in the austenite matrix. Moreover, the 3650 cladding surface provided greater wear resistance than rail steel and not much difference in hardness, which is suitable for rail maintenance in a realistic situation.

Abstract: This study examines the properties of laser coatings applied to structural steel using 316L stainless steel to enhance corrosion resistance. It compares conventional laser cladding with the Extreme High Speed Laser Cladding (EHSLC) method. Six samples were produced, with Sample 1 using conventional cladding and Samples 2 through 6 using EHSLC with varying parameters. The hardness of the layers varied significantly, with conventional cladding showing the lowest hardness (below 200 HV 0.1) and EHSLC samples reaching up to 600 HV 0.1. These differences are attributed to microstructural variations: austenitic structures had lower hardness and good corrosion resistance is assumed, while martensitic structures exhibited lower chromium and nickel content, leading to different mechanical properties and probably reduced corrosion resistance. The results highlight the importance of parameter selection in EHSLC for optimizing the performance of treated parts.

Abstract: Using of metal matrix composite coating is a promising approach for improving the surface properties of a component against the mechanical and environmental attacks especially wear and corrosion. Laser cladding (LC), also known as direct energy deposition (DED), is an additive manufacturing (AM) technique, able to perform coating, repair worn parts, manufacturing and prototyping. In this work, pure Al and a mixture of multi-ceramic Al-15SiC-15Al₂O₃ coatings were successfully deposited on Al-based substrate. The quality of the deposited clads was evaluated according to macro-graphic, microstructure, and microhardness characteristics. The microscopic inspection of the multi-ceramic coatings showed a slight dilution of SiC particles. Also, XRD investigation revealed a formation of Al₄C₃ carbide. Besides SiC and Al₂O₃ hard phases, this yielded an increase in matrix microhardness about 180% (from 75 to 212 Hv_0.05) as compared to pure Al clads, indicating a great improvement in the mechanical properties of the composite cladded coating.

Abstract: Stainless steels as one of the most appealing structural material in many fields of industries because of its resistance to corrosion, high tensile strength, durability, temperature resistant etc. To improve its surface properties and overcome issues like large heat affected zones, poor surface quality, and limited dissolvability, researchers have explored surface modifications through laser cladding. This paper gives a detailed review about the work done in recent years, in the region of laser cladding of different grades of stainless-steel alloys with different coating materials highlighting on feeding ways of cladding material, laser cladding process parameters, types of lasers employed, types of coating & composite coating materials in enhancing the surface properties of the stainless-steel substrate and their relevant applications.

Abstract: Laser cladding of a Ni based powder on cast iron is performed by a 4kW continuous diode laser. For this, a robot programming method named “Wavering” is used. Indeed, this method allows to cover large surfaces (width higher than 5 mm and thickness higher than 4 mm). The cast iron substrate used during this work is employed for its thermal properties in glass mold Industry. However, it has drawbacks which are weak wear, corrosion, and abrasion resistance. Conventional techniques used to protect the molds, like Plasma Transferred Arc (PTA), affect the molds microstructure, but also the thermal and mechanical properties. The laser cladding of the Ni based alloy allows to protect the molds without affecting the cast iron thermal properties (low Heat Affected Zone). The purpose of this research is to produce a well bonded Ni based melted powder without pores or cracks on large and curvilinear surfaces. First, the coating, adapted to this substrate geometry, is optimized. Then, an investigation of the impact of the processing parameters (power, scanning speed and wavering frequency) on the microstructure is carried out. Besides, the mechanical behaviour is analysed by microhardness. In addition, the evolution of the Heat Affected Zone (HAZ) according to the processing parameters is observed. Two kinds of areas are inspected in terms of microstructure: a stable area obtained after a single pass and an interferenced area linked to superimposed passes. Those analyses led to a cladding parameter optimization to obtain perfect bonding, to avoid porosity propagation and to limit the HAZ emergence on curvilinear surfaces. Finally, in comparison with the PTA technique, it appears that laser cladding process with wavering method leads to a good coating of curvilinear surfaces.

Abstract: The present research shows the possibility of using an ytterbium nanosecond pulsed fiber laser for wear resistance improvement of carbon and alloy steels. The wear test was performed in accordance with the block-on-ring scheme with dry sliding friction on a friction machine. Surface dispersing/alloying was carried out from a boron carbide paste. This leads to a significant wear resistance improvement of steels. It was revealed that the mass loss during wear test reduced by several times after laser treatment compared to the non-treated samples. The wear mechanism differs depending on the type of steel and largely refers to their microstructure and composition. The tribo-oxide layer forms during the wear test.

Abstract: Slurry pumps in the mineral processing industry are parts that erode very quickly. Erosion is predominantly caused by abrasion from fine particles of the ores. Because of this, the erosion process takes place on impeller blades and cover plates that directly contact the slurry. This paper evaluates the wear of laser-coated pump parts in the mineral processing industry. Building upon previous research conducted by the authors, we aimed to determine the best laser coating powder system to extend the useful life of specific laser-coated pump parts. Four blades of a slurry pump impeller were each treated with a different laser powder coating, then assessed for wear after 19 days of operation. During this real-life trial, each powder system performed differently. The laser coatings were worn away in two general directions. The first direction was along with the blade pattern, and the second wear direction was from the center of the impeller to the direct blade surface. Partial surface cladding led the material to wear away faster than complete surface cladding due to perpendicular force. Based on these results, in order to use material hardness and wear resistance to higher efficiency, we need to cover all surfaces with different thicknesses depending on the wear rate of the part. This study also showed that Powder System 2 was the most suitable coating material for this type of slurry pump.

Abstract: Preparation of titanium alloy coating on the low carbon steel surface is an effective way to ensure the service performance of steel in marine environment. In this work, the effect of Cu interlayer thickness on the microstructure and properties of the titanium alloy coating was systematically studied. The results showed that a thin Cu interlayer cannot inhibit the diffusion of iron, and the Fe-Ti intermetallic compound (IMC) layer at the coating/substrate interface weakens the bonding property of the coating. And iron compounds on the surface of the coating surface are negative for corrosion resistance. The thickening of Cu interlayer inhibits the diffusion of iron and increases the shear strength of the coating by 40%～60%. When the iron compound is not present on the coating surface, the optimal electrochemical properties of the titanium alloy coating were achieved. However, the excessive thickness of the Cu interlayer will accelerate the heat loss of the molten pool and lead to the fusion defect in the initial cladding stage. In this study, the optimum thickness range of Cu interlayer (290μm ~ 375μm) was obtained. When the interlayer was in this range, titanium alloy coatings with excellent comprehensive properties could be prepared.

Abstract: In laser cladding process, generation of high temperature gradients significantly impacts the output coating parameters such as mechanical and microstructural properties. Buffer layer addition between hard alloys cladding shows reduction in crack formation and also dilution rates. The present study is on Insitu temperature monitoring in laser cladding of Stellite 6 alloy with addition of buffer layer, which were compared with direct deposition of Stellite 6. The results show about 17 - 20 % low substrate temperatures with a buffer layer, indicates more uniform cooling of the hard coatings than direct cladding. The increase in laser power measures 35 - 40 % higher temperatures in both the cases due to large heat addition at the clad region. The study provides an insight into the substrate temperature evolution in cladding with and without a buffer layer.

Abstract: Nickel-aluminum bronze coatings were deposited on high strength stainless steel SUS630 by laser cladding. The microstructure of the multi-layer structures was investigated. The OM results showed that steel-bronze bimetallic materials were successfully fabricated without any defects. The dilution rate of substrate can be adjusted by controlling the laser parameters. The main phases of the coating are α-Cu, Fe-rich dendrites and κ phases. Tensile tests were carried out and it was found that the upper specimen with fewer Fe-rich related components had better tensile strength properties.