Ni-based Matrix Research Articles

Additively Manufacturing Mining Tools

Abstract Additive manufacturing techniques give the mining industry a chance to revolutionize the conceptualization, prototyping, and production of mining tools, including using WC-Fe, Ni-based matrix coatings that display exceptional properties. The article includes a case study involving the successful utilization of WC-NiCrBSi mixed powder as a protective coating on AISI 9310 steel components to enhance wear resistance and durability for mining tool applications.

Improving the Electrocatalytic Performance for the Hydrogen Evolution Reaction in the Electrodeposited Ni-Based Matrix by Incorporating WS2 Nanoparticles

Ni based alloys and composites may constitute an alternative to noble metal as a catalyst for the hydrogen evolution reaction (HER) during the water electrolysis. The aim of the present study was to evaluate the electrocatalytic activity of the electrodeposited Ni-WS2 and Ni–Mo–WS2 composites. The effect of the addition of WS2 nanoparticles on the structure, surface morphology and surface composition of Ni and Ni–Mo metallic matrix was thoroughly examined. The obtained results were used to explain the catalytic performance and the HER mechanism of the studied composites. It was found that the incorporation of the WS2 nanoparticles increased the electrocatalytic activity of the Ni and Ni–Mo matrix. The highest electrocatalytic activity was found for the Ni–Mo–WS2 electrode. This was, firstly, a consequence of the quasi-amorphous structure of the composite, which increased the real surface area of the electrode. On the other hand, the intrinsic catalytic activity was enhanced by the outer oxide layer rich in Mo oxides formed on the surface of the composite electrode. The presented research is an important contribution to the design of the non-precious composite electrodes for the HER.

Effect of variation of ceramic reinforcement content on metallurgical and cavitation erosion behaviour of microwave processed composite clads

The effect of varying (0%-30% by weight) reinforcement (Cr3C2) on the different characteristics of microwave processed composite clads (Ni-based (EWAC) matrix) was determined. The microstructure of composite clads showed growth of randomly orientated lamellar bands (Cr-Fe-C) rich phase in the Ni-Fe-Cr rich matrix, which confirmed the metallurgical bonding of clads with substrate. Higher microhardness values, with a lower standard deviation, were observed in the 30% Cr3C2 reinforced clad. Excellent cavitation erosion resistance of EWAC + 30% Cr3C2 composite clads, among all other clads and substrate samples, was observed. Synergy of higher microhardness and toughness resulted in significant improvement in the cavitation erosion resistance. Formation of pits, craters and plastic deformations were mainly responsible for the cavitation erosion failure of clads and substrate samples. The transition of damage from ductile mode to dual (brittle and ductile), and further brittle mode was observed with increase in weight percentage of reinforcement.

Vacuum brazed Ni-based coating reinforced with core-shell WC@Cu/Co-P

Improving the wettability and bond strength of WC with Ni-based matrix and preventing the growth of WC in the melt of Ni-based alloy are always the challenges that should be considered in the fabrication of Ni/WC infiltration brazed coatings. In this research, to improve interface in Ni/WC infiltration brazed coatings, a thin shell of Cu/Co-P was employed. The shell had a thickness of about 80 nm and it was deposited on WC powders by electroless plating. The morphology of WC@Cu/Co-P powders and its microstructure as the reinforcement phase in Ni-based matrix were characterized by field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, and X-ray diffraction. The results showed that this proposed coating had very low porosity, resulting a dense free porosity coating with homogenous distribution of WC. Also, the average growth rate of WC@Cu/Co-P particles was approximately 75 % lower than the same figure for the bare WC particles during liquid phase sintering. These results led to a desirable wear property; the pin on disk test was carried out to investigate the wear behavior of coatings. The wear rate reduction was reduced by 52 % compared to the coatings processed without the shell layer. The average hardness of WC@Cu/Co-P/NiCrBSi coatings was reported about 1590 Vickers, which is 30 % higher than the average hardness of conventional WC/NiCrBSi coatings.

Phase composition and fatigue crack growth behavior of Inconel 718 under additive manufacturing

AM samples both in as-deposited and heat-treated states have been subjected to microstructural and phase characterization. Mechanical testing has been performed to heat-treated samples with respect to the build directions. AM samples were made by Direct Laser Deposition under the three different levels of efficient energy from Inconel 718 powder. As-deposited samples contained dispersed particles of Fe2Ti Laves phase, NbC and NbNC as well as starting clusters of γ′ phase. Although the standard heat treatment at 980 °C was found to result in partial dissolution of Laves phase precipitation of δ phase occurred around it. Depletion in Nb of Ni-based matrix due to formation of NbC, NbNC and Laves phase in as-deposited states causes precipitation of γ′ phase as the main strengthening phase in heat-treated states. Fatigue crack propagation manners were analyzed with fractography. Fine columnar dendrite structure of samples tested in parallel build direction to the loading is much more resistant to fatigue crack propagation. Fatigue crack bypass dispersed Laves phase which is fixed in matrix by δ phase.

Corrosion behavior of laser-cladding NiCrBSi coating in molten aluminum alloy

In order to investigate the corrosion mechanism in molten aluminum alloy, NiCrBSi coating was prepared on H13 tool steel by laser-cladding. The coating mainly contained γ-(Ni, Fe), Cr7C3, Ni3B, and CrB. Floret-shaped CrB and dendritic Cr7C3 were uniformly distributed in the Ni-based solid solution matrix, with Ni-Ni3B network eutectics separated around them. The corrosion test results in molten aluminum alloy at 1073 K revealed that NiCrBSi coating exhibited excellent corrosion resistance, which was attributed to its boride-containing phase composition and microstructure. Borides can help prevent the coating surface from being wetted by liquid aluminum at the early stage of corrosion. With the prolongation of the corrosion time, molten aluminum alloy began to wet the coating surface and react with it to form a transition layer. However, the dense network structure formed by CrB hard phases and boron-rich eutectics can effectively prevent liquid aluminum from intruding into the interior part of the coating. Meanwhile, the raised borides at the interface can also slow down the reaction between aluminum and the surrounding Ni-based matrix. Thus, the corrosion rate was relatively slow and a transition layer with the thickness of 140 μm was formed after 150 h of corrosion, while the inferior coating and H13 substrate still remained intact.

Microstructure and properties of Ni-WC gradient composite coating prepared by laser cladding

In this study, an Ni-based gradient composite coating reinforced with WC was prepared on a Q345R steel substrate by laser cladding. The Ni-WC composite coating was designed as a multilayer structure with gradient composition. The coating started with a layer of C276 alloy with 10 wt% WC on the substrate, and the subsequent layers were composed of Ni60 alloy with different WC contents (10, 30, and 50 wt% WC). The overall morphology, phase composition, and microstructure of the coatings were investigated. The microhardness and the wear properties of each layer of the coatings were also evaluated. The results showed that the gradient composition design was beneficial for reducing the cracking tendency. The coating was composed of an Ni-based matrix, WC, and multiple carbides and borides hard phases. With increasing WC content in the layers, the hard phases exhibited regional distribution characteristics. The WC reinforcement particles underwent different types of dissolution during the cladding process. From the surface to the substrate, the average microhardness of the coating was 1053.5 HV0.2, 963.4 HV0.2, 859.0 HV0.2, 441.7 HV0.2, and 260.5 HV0.2. The wear tests revealed that the coefficient of friction and the wear loss values of the four layers were all lower than those of the substrate, demonstrating enhanced wear resistance.

Novel investigation on tribological behavior of microwave synthesized functionally graded claddings

In this study, functional performance of Ni/Cr3C2 functionally graded claddings (FGCs) was investigated under dry sliding wear environment. The Ni/Cr3C2-based FGCs were produced by varying Cr3C2 fraction (Ni-XCr3C2) (X=10%–30% by weight) using microwave irradiation. The FGC layers were composed of cellular-structure with reinforced particles dispersed randomly inside Ni-based matrix. Variation of Cr3C2 particles inside Ni matrix exhibited significant impact on micro-structural and mechanical properties. The microhardness profile of the FGC layers showed an increase in hardness value with an increase in the amount of reinforced Cr3C2 particles. FGC top layers showed the maximum value of micro-hardness of 555 ± 34 HV. Functional performance of microwave processed FGCs was studied through the pin-on-disk tribometer under varying sliding velocity and sliding distances. For comprehension study, wear study was also carried out on microwave processed single layer clads with compositions corresponding to FGC layers. The FGC sample showed better wear resistance than all single clad layers and substrate material. The FGC sample exhibited 1.6 times less wear rate than the Ni-based + 30% Cr3C2 single layer clad. The worn-out surfaces of FGC and single-layer-clads showed presence of multiples cracks and grooves, which resulted in their weight loss during dry sliding contact. Material debonding and the formation of craters and cracks are the main phenomena responsible for the wear loss in the FGC surface.

Effect of Laser Processing Parameters on Microstructure, Hardness and Tribology of NiCrCoFeCBSi/WC Coatings.

In the present study, pulsed laser post-processing was applied to improve the properties of the thermally sprayed NiCrCoFeCBSi/40 wt.% WC coatings. The powder mix was deposited onto a mild steel substrate by flame spray method and then the as-sprayed coatings were processed by Nd:YAG laser. The peak power density applied was between 4.00 × 106 and 5.71 × 106 W/cm2, and the laser operating speed ranged between 100 and 400 mm/min, providing processing in a melting mode. Scanning electron microscopy, energy dispersive spectroscopy, Knop hardness measurements, and “ball-on-disc” dry friction tests were applied to study the effect of the processing parameters on the geometry of laser pass and microstructure, hardness, and tribology of the processed layers. The results obtained revealed that pulsed laser processing provides a monolithic remelted coating layer with the microstructure of ultrafine, W-rich dendrites in Ni-based matrix, where size and distribution of W-rich dendrites periodically vary across remelted layer depth. The composition of W-rich dendrites can be attributed to a carbide of type (W, Cr, Ni, Fe)C. The cracks sensitivity of coatings was visibly reduced with the reduction of power density applied. The hardness of coatings was between ~1070 and ~1140 HK0.2 and correlated with microstructure size, being dependent on the processing parameters. The friction coefficient and wear rate of coatings during dry sliding were reduced by up to ~30% and up to ~2.4 times, respectively, after laser processing.

Slurry Erosion Performance of Ni + xCr7C3 Microwave Composite Clad with [10–30 wt%] Cr7C3 Content

In the present study, a series of Ni + xCr7C3 (x is the weight fraction of the Cr7C3) clads on hydro turbine steel (CA6NM) were developed through microwave cladding. The weight fraction of Cr7C3 was 10 wt%, 20 wt%, and 30 wt% in the developed clads. These clads were developed to mitigate the erosion induced degradation of the substrate surface. The Ni + 10% Cr7C3 composite clad exhibited poor erosion characteristics compared to Ni-based (Ni + 0% Cr7C3) clad due to embrittlement of the Ni-based matrix caused by dissolution of reinforced Cr7C3 particles. Maximum erosion resistance was exhibited by Ni + 30% Cr7C3, followed by Ni + 20% Cr7C3 clad. The enhanced slurry erosion performance of Ni + 30% Cr7C3 clad can be related to increased volume fraction of Cr7C3 carbides and other secondary phases, such as M7C3, Ni2Si. The average microhardness and fracture toughness of Ni + 30% Cr7C3 clad was on the order of 756 ± 37.8 HV and 12.9 ± 0.64 MPa√m, respectively. Analysis of eroded surface indicates that Ni + 30% Cr7C3 clad exhibited an optimum combination of hardness and fracture toughness for mitigation of slurry erosion.

Effect of adding soft Bi2O3 on structural modification and tribological regulation of Ni-5 wt% Al composite coating in wide temperatures range

An alternative process to fabricate Ni-5 wt% Al-Bi2O3 composite coatings was developed through the atmospheric plasma spraying technique. The influence of soft Bi2O3 additions on tailoring microstructure and tribological behavior of resulting Ni-5 wt% Al-Bi2O3 composite coating was investigated over a broad range of temperatures. As the Bi2O3 inclusion within the Ni-based matrix gradually increased, the obtained Ni-5 wt% Al-Bi2O3 composite coatings featured as the increasingly compact laminated hierarchy. This was, however, compromised with no significant improvement in mechanical capabilities. All Ni-5 wt% Al-Bi2O3 composite coatings demonstrated the temperature-mediated frictional characteristic. Nevertheless, wear aggravation occurred for as-received composite coatings at the medium temperatures. It was noteworthy that Ni-5 wt% Al-Bi2O3 composite coatings entailed superior lubrication at 800 °C, which was intrinsically associated with the lubricious constituents primarily consisting of Bi2O3 and NiO on the sliding surface. The influential factor of temperature and Bi2O3 on varying friction and wear for Ni-5 wt%. Al-Bi2O3 composite coating was discussed from the perspective of tribochemically oxidative interactions between the rubbing contacts.

Considering Impact and Corrosion Resistance in the Performance of Heavy Wear Resistant Coatings

Laser clad coatings consisting of a Ni-based matrix and tungsten carbide (WC) hard phases are used for heavy wear protection of components in many industries. Matrix composition and WC type can be chosen to give these composites resistance to erosive/abrasive wear, as well as to the impacts of particles and corrosion. Maintaining ductility in the matrix is important, so that it can absorb impact energy and minimize cracking, thus avoiding penetration of corrosive media through cracks and subsequent corrosion in the substrate-cladding interface. Claddings were tested for their impact resistance by means of a single impact with a hard, spherical indenter. The depth of impact craters was measured, and the cracking behavior was analyzed. Corrosion resistance of Ni/WC composites, a HVOF WC/CoCr coating and a hard chrome reference coating were tested by electrochemical corrosion in a 3.5 wt.% NaCl solution and by exposure for up to 1000 h in a salt spray test.

Precipitation behavior of M23C6 carbides and its effect on mechanical properties of Ni-based Alloy 690

ABSTRACT The effect of solution annealing and aging treatment on the intergranular carbide precipitation behavior of alloy 690 tubes for steam generators is investigated. The carbides precipitated on the grain boundaries were identified as chromium-rich M23C6 carbide, which has a cube-cube orientation relationship with the matrix on one side of neighboring grains. The carbide precipitation behavior is closely related to the interaction between the solubility of carbon in Ni-based matrix and diffusion of alloying elements. The ultimate tensile strength and elongation of the solution annealed alloy 690 tubes at 300°C are 638.8 ± 12.4 MPa and 43.2 ± 4.2%, respectively. In the early stage of precipitation, the ultimate tensile strength increased to 720.4 ± 13.5 MPa. The carbides function as reinforcement in alloy 690 and provide strength enhancement with aging time reached 15 hours. However, when the aging time passed 15 hours, this property gradually decreased to 710.6 ± 12.6 MPa due to the low bonding strength between the carbide and matrix.

Phase, Composition and Structure Changes of CoCrNi-Based Concentrated Alloys Resulting from High Temperature Oxidation.

In this work, CoCrNi, FeCoCrNi and CoCrFeMnNi concentrated alloys with a Y-Ti oxide particle dispersion were prepared by mechanical alloying and Spark Plasma Sintering. The alloy consists of an FCC Ni-based matrix with a Y-Ti oxide dispersion and additional phases of Cr23C6 and Cr2O3. The effect of Fe, Mn, and Y-Ti oxide particles on the formation of oxide scales and the composition of the adjacent CoCrNi and FeCoCrNi alloys was studied. It was found that alloys without Mn in their composition form a protective Cr2O3 scale. The Cr23C6 particles provide an alternative mechanism for balancing the chromium loss during the oxidation. Y and Ti from the oxide particles participate in the formation of the protective oxide scales. Fe promotes Y and especially Ti diffusion through the Cr2O3 scale, resulting in the formation of Ti-depleted regions in the alloy. The findings will serve for the further development of these new materials.

A comparative study on the tribological behavior of various thermally sprayed Inconel 625 coatings in a saline solution and deionized water

In this study, thermally sprayed Inconel 625 coatings were used to improve the corrosion-wear resistance of 304L stainless steel substrates in saline environments. The tribological behavior of various Inconel 625 coatings obtained through flame spraying (F), arc spraying (A), plasma spraying (P), or high-velocity oxygen fuel spraying (H) was evaluated by testing the specimens on a pin-on-disk apparatus with a cup-shaped container that was filled with a 5 wt% NaCl solution or deionized (DI) water. The results indicated that regardless of the testing solution, the corrosion-wear resistance of the Inconel 625 coating specimens was in the order F > A > P > H. Microstructural examination revealed that the oxide within the as-sprayed Inconel 625 coating layer was mainly Cr2O3 and exhibited a higher hardness but lower elastic modulus than the Ni-based matrix. The oxide within the Inconel 625 coating layer is suggested to function as an antiwear phase against the corrosive-wear environment. The high corrosion-wear resistance of the F specimen was attributed to the high oxide content within its coating layer. In addition, all Inconel 625 coatings exhibited higher wear resistance in the 5 wt% NaCl solution than in the DI water, which implied that chloride lubricated the sliding wear, considerably reducing weight loss of the coating after corrosion wear.

Slurry Erosion Performance of Ni + B4C Microwave Composite Clads

Abstract A composite clad of Ni-based alloy and B4C was developed on austenitic steel substrate through microwave hybrid heating. The B4C was added with Ni-based alloy powder in various weight proportions (0%, 5%, 10%, and 20%). The clads were investigated for the microstructural details, nanohardness and slurry erosion performance. Silt collected from river Uhl was used as the erodent for the slurry erosion test. Slurry erosion performance of the clads was evaluated at an impact angle of 90 deg and jet velocity of 40 m/s. Microstructural characterization confirms the uniform distribution of hard (boride and carbide) phases in the Ni-based matrix of the microwave composite clads. The presence of hard phases in the Ni-based matrix enhanced the slurry erosion resistance performance.

Influence of tungsten coating on microstructure and thermal damage of brazed diamonds

ABSTRACTDegradation of diamond strength resulting from thermal damage in vacuum brazing process constrains the application of Ni-based brazed diamond tools. To reduce the thermal damage to brazed diamonds, the effectiveness of coating diamond with tungsten was investigated by scanning electron microscopy, Raman spectroscopy and friability test. Tungsten coating was deposited on diamond surfaces by vacuum diffusion method. The experimental results show that tungsten coating, as a buffering layer, plays a stress-relaxing role and brings about fewer cracks in the Ni-based matrix near diamond grains. Graphitization of W-coated diamond after brazing is much slighter than that of uncoated diamond and Ti-coated diamond, according to the morphology and Raman spectra. The isolation of diamond from nickel catalyst by tungsten coating inhibits the graphitization of diamond, which can further explain the increase in the toughness index of brazed diamonds.

Infiltration brazed core-shell WC@NiP/NiCrBSi composite cladding

In this study, a novel Ni-P-coated WC/NiCrBSi composite cladding was prepared on a carbon steel substrate through high-temperature vacuum brazing technique with the aim of improving the wear properties of the surface. In order to improve the wettability of WC particles by a liquid phase (NiCrBSi alloy), Ni-P layer was deposited on carbide particles by electroless plating. This layer assisted to fabricate a thick coating with very low porosity, improving adhesion strength between ceramic particles and the matrix. The morphology, crystal structure and microstructure of coated carbides and the resultant composite cladding were characterized by field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analysis. Thin electroless plated Ni-P shell with a thickness about 50–150 nm, were coated on WC particles. In the claddings, a uniform and homogenous distribution of WC particles in Ni-based matrix was observed. The pin on disk wear test was carried out to investigate the wear behavior of the fabricated cladding reinforced with and without Ni-P coated WC particles. The results indicated that the resistance against crack initiation and propagation significantly improved by using Ni-P layer in the sintered cladding. This cladding exhibited very low wear weight loss than conventional brazed cladding.

Thermal characteristics and amorphization in plasma spray deposition of Ni-Si-B-Ag alloy

Abstract Crystalline-amorphous matrix composites preserve the amorphous material high strength and additionally gains on plasticity. Substituting hard crystalline precipitates with soft ones should even more improve the latter. Therefore, this work was aimed at verifying, whether Ag and Ni-Si-B alloy shows liquid immiscibility and consequently, if they might form crystalline Ag/Ni-Si-B amorphous/crystalline composite. Firstly, a mixture of 95 wt% of Ni-Si-B (1559-40) and 5 wt% of Ag powders was arc-melted in argon and cooled at copper plate. The solidification process was documented by IR mid-wave camera and Time/Temperature graph. The microstructure of the ingot was studied using a scanning electron microscope (SEM) and light microscope (LM). Secondly, the powders mixture was plasma sprayed on a cooled copper plate. The cross-section microstructure and the phase composition of the plasma spray deposit were analyzed with a transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffractometer (XRD). The thermal characteristics of the plasma sprayed deposit and the Ni-Si-B powder were analyzed using differential thermal analysis (DTA) and compared. The results show that the melted Ag and Ni-Si-B powders form immiscible liquids at high temperatures used both during arc-melting and plasma-spraying. The proved that that the plasma spraying enables production of a Ni-Si-B/Ag composite with high strength Ni-based matrix with dispersed in it fine soft Ag-FCC flake-like particles.

Ordering Transformation and Age Hardening in a Ni-Cr-W Superalloy

The microstructural changes occurring in a Ni-Cr-W superalloy during prolonged exposure to proper temperature have been investigated using transmission electron microscopy. It is demonstrated that nanometer-sized C11b (Pt2Mo-type) and DO22 superlattices can precipitate in the Ni-Cr-W alloy by means of a simple aging treatment at temperatures varying in the range of 773 K to 973 K (500 °C to 700 °C). The mechanism of transformation to long-range order has been revealed to accord with continuous mode based on transmission electron microscopy results and variation trend in Vickers microhardness. No signs of overaging and coarsening of C11b and DO22 phases with further aging have been found, which indicates that both of them have a high-thermal stability. The orientation relationships and interfaces between C11b/DO22 precipitates and Ni-based matrix have been investigated by high-resolution transmission electron microscopy, and the results reveal that the interfaces between C11b/DO22 precipitates and surrounding matrix are coherent at the atomic scale. Because of the high-density nanometer-sized C11b/DO22 precipitates, the microhardness of the alloy is improved remarkably.