IN625 is a nickel-based super alloy with remarkably high temperature corrosion resistance, which makes it a good choice for marine and chemical industry applications. However, its relatively low hardness and low wear resistance limit its applications in many areas. In order to increase hardness and wear resistance of laser cladded IN625 coating, B4C nanoparticles were used to reinforce the cladded coating. B4C nanoparticles and IN625 powder were alloyed mechanically under the work of high-energy ball milling. Laser cladded samples were tested for hardness and high temperature friction and wear. OM, XRD, SEM, EDS and EPMA were used for analyzing the microstructure, elemental distribution and wear morphology. The B-C-Cr phase of the powder was produced by high-energy ball milling. The precipitation of Ni3B and Cr3C2 phases in the interdendritic region, refined dendritic structure. The results demonstrated that cladded coating without cracks can be obtained when the B4C nanoparticles content is less than 2 wt%. Elemental analysis showed that the boride reinforced phase was distributed uniformly along a boundary in a molten pool to form B-enriched belts. Mechanical tests showed that the hardness of reinforced layers were increased by about 64% and the high temperature wear volume of B4C nanoparticles reinforced coating was decreased by about 86% compared to the pure IN625 coating.

Effect of B4C nanoparticles on microstructure and properties of laser cladded IN625 coating

Since current trends in the transportation, energy or mechanical industries impose increasingly demanding service conditions for metallic parts, metal matrix composites (MMCs) are the object of a growing interest. Powder-based laser additive manufactur‐ ing, which allows making parts with complex shapes, appears particularly adapted for the production of MMCs. This paper reviews the current state-of-the-art in the produc‐ tion of MMCs by additive processes, with the aim of assessing the potentials and difficulties offered by these techniques. Two main processing routes are envisaged, i.e. (1) the processing of ex situ composites in which the reinforcing phase as a powder—often of ceramic particles—is directly mixed with the powder of the matrix alloy, and both powders are simultaneously processed by the laser. (2) Alternatively, the reinforcing phase can be produced in situ by a chemical reaction during the fabrication of the composite. For both processing routes, a careful control is needed to overcome challenges brought, e.g. by the behaviour of the reinforcement particles in the laser beam, by changes in laser absorp‐ tivity or by the dissolution of the reinforcing particles in the molten metal, in order to produce MMCs with enhanced usage properties.

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On the Role of Interfacial Reactions, Dissolution and Secondary Precipitation During the Laser Additive Manufacturing of Metal Matrix Composites: A Review

Ni- and Fe-based composite coatings were laser cladded on 40Cr steel to improve the surface mechanical property and corrosion resistance, respectively. The microstructure and phase composition were analyzed by x-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) equipped with an energy-dispersive spectrometer (EDS). The micro-hardness, tribological properties and electrochemical corrosion behavior of the coatings were evaluated. The results show that the thickness of both the coatings is around 0.7 mm, the Ni-based coating is mainly composed of γ-(Ni, Fe), FeNi3, Ni31Si12, Ni3B, CrB and Cr7C3, and the Fe-based coating is mainly composed of austenite and (Fe, Cr)7C3. Micro-hardness of the Ni-based composite coating is about 960 HV0.3, much higher than that of Fe-based coating (357.4 HV0.3) and the 40Cr substrate (251 HV0.3). Meanwhile, the Ni-based composite coating possesses better wear resistance than the Fe-based coating validated by the worn appearance and the wear loss. Electrochemical results suggested that Ni-based coating exhibited better corrosion resistance than the Fe-based coating. The 40Cr substrate could be well protected by the Ni-based coating.

A Comparative Study of the Microstructure, Mechanical Properties and Corrosion Resistance of Ni- or Fe- Based Composite Coatings by Laser Cladding

Influence of exposure at high temperature on the local scratch mechanisms in laser cladded Inconel 625-base metal matrix composite coatings

This paper deals with the influence of laser surface texturing on tribological performance of two different tool steels: (a) Bohler K100 produced by conventional production technology and (b) Bohler K390 Microclean® produced by powder metallurgy. The surface of heat-treated tool steels was modified using three different texture patterns. Impact of laser surface texturing was analyzed after different treatments. Furthermore, selected samples were borided to evaluate the combined influence of laser surface texturing and boriding on tribological performance of surface-treated samples. The results show that boriding was not beneficial for wavy surface type, and the steel production technology had a certain influence on the spinning tool. The laser surface texturing had an effect on decreasing the coefficient of friction on the K100 tool steel; however, it did not influence the tribological performance of the K390 Microclean® tool steel. Boriding process was efficient in decreasing the coefficient of friction for both steels. The low coefficient of friction values did not have a positive influence on the wear depth.

Influence of Laser Surface Texturing on Tribological Performance of Tool Steels

The present study focuses on the effect of different Cr/C ratios on the microstructure, microhardness, and corrosion resistance of Ni-based laser clad hardfacings, reinforced by in situ synthesized chromium carbide particles. Cr3C2-NiCr composites have been laser processed with graphite/Cr/Ni powder blends with varying Cr/C ratios. Following phase analysis (x-ray diffraction) and microstructure investigation (scanning electron microscopy; energy dispersive x-ray analysis; transmission electron microscopy), the solidification of laser melt pool is discussed, and the corrosion resistances are examined. Several different zones (planar, dendritic, eutectic and re-melt zone) were formed in these samples, and the thicknesses and shapes of these zones vary with the change of Cr/C ratio. The sizes and types of carbides and the content of reserved graphite in the composites change as the Cr/C ratio varies. With the content of carbides (especially Cr3C2) grows, the microhardness is improved. The corrosive resistance of the composites to 0.2M H2SO4 aqueous solution decreases as the Cr/C ratio reduces owing to not only the decreasing Cr content in the NiCr matrix but also the galvanic corrosion formed within the carbide and graphite containing Ni matrix.

Effect of Cr/C Ratio on Microstructure and Corrosion Performance of Cr3C2-NiCr Composite Fabricated by Laser Processing

The invention relates to a laser forming method of a WC (Wolfram Carbide)-metal composite material structural component. According to the formula, raw material powder used in the laser forming method comprises the following components in percentage by weight: 15-45% of WC, 0.4-5% of W, 0-7% of Ni, 0-27% of Cr, 0-10% of Mo, 0.1-1.2% of rare earth oxide and of the balance being metal. The powder for laser forming is quantitatively prepared and mixed by using a double-hopper spiral powder feeding and mixing system; the double-hopper spiral powder feeding and mixing system mainly comprises double hoppers, an electric powder feeding screw rod, a direct-current stepping motor, a powder fluidization machine and a powder outlet channel; a coaxial discontinuous powder nozzle is adopted as a nozzle for laser forming; by utilizing the control of the powder feeding and laser, layered structures of the inner and outer parts of a composite part are formed; the mechanical property of the composite material can reach more than 80% of a matrix metal material.

Laser forming method of WC (Wolfram Carbide)-metal composite material structural component

The invention relates to a novel laser formation of a TiC-NiMo composite component A raw material formula of raw powder used in the method comprises the following raw materials in percentage by weight: 512 to 645wt% of graphite, 2248 to 2780wt% of Ti, 478 to 871wt% of Mo, 024 to 069wt% of rare earth oxide, and the balance Ni According to the method, the quantitative conveying and mixing of the powder used for laser forming are carried out through a multi-hopper spiral powder conveying and mixing system; a coaxial discontinuous powder spraying head is used as a nozzle for the laser forming; the system is used for controlling the powder conveying and the laser, thus the formation of layering structures of the inner part and the outer part of a composite part can be achieved; the mechanical property of a composite can exceed 60% of that of a base metal material

Laser formation method of TiC-NiMo composite component

Purpose




The original powder commonly used for laser 3D printing is atomized alloy powder. The purpose of this study is to investigate the effect of ball milling (BM) on the structure and performances of the alloy powder and its composite products.




Design/methodology/approach




BM powder of Ni-Cr-graphite elements was subjected to laser cladding forming and the effect of BM on the powder structure was studied by X-ray diffraction, metallographic microscopy and scanning electron microscopy. The laser cladding-formed coatings were also tested by reciprocating friction measures and electrochemical corrosion experiment.




Findings




The results showed that the grains of laser cladding-formed Cr3C2-NiCr coating of BM powder were more refined compared to the coating of the atomized powder. Moreover, the abrasion resistance and corrosion resistance were slightly improved.




Originality/value




This work offers guidance for new original powder selection for laser 3D printing/powder bed forming/selective laser melting applications.

Chunlin He

Papers

Effect of Cr/C Ratio on Microstructure and Corrosion Performance of Cr3C2-NiCr Composite Fabricated by Laser Processing

Laser forming method of WC (Wolfram Carbide)-metal composite material structural component

Laser formation method of TiC-NiMo composite component

Effect of ball milling on the microstructure and performances of laser clad forming Cr3C2-NiCr composites