Hardness Enhancement Research Articles

Enhancing geometric integrity and surface hardness of SLM-printed Ti-6Al-4V components with support structures and laser nitriding

This study investigated the effect of support structure and post-processing surface nitriding on high aspect ratio Ti-6Al-4V components fabricated using Selective Laser Melting (SLM). It examined changes in geometric integrity, porosity, and mechanical properties. Samples were printed without support structures (S1) and with support structures (S2). After SLM printing, both samples underwent open-air laser nitriding at duty cycles (DC) ranging from 50 % to 100 %, aiming to create crack-free nitride layers to increase surface hardness. The results indicated that support structures effectively mitigate thermal-induced deformation, with S2 exhibiting minimal warping and closer adherence to design specifications than S1. Although S2 showed increased porosity as revealed by X-ray Computed Tomography (XCT), its refined microstructure contributed to increased hardness. Optical Microscope and Scanning Electron Microscope (SEM) analyses demonstrated that laser nitriding at a 50 % duty cycle produced uniform, crack-free titanium nitride (TiN) layers. Vickers hardness tests revealed a significant enhancement in the surface hardness of both laser-nitrided samples, with S2 displaying finer TiN dendrites that further improved its surface hardness. The use of support structures was found to be effective in achieving a more uniform microstructure and enhanced hardness in the nitride layer.

Enhanced microstructures, mechanical properties, and machinability of high performance ADC12/SiC composites fabricated through the integration of a master pellet feeding approach and ultrasonication-assisted stir casting

Integrating ceramic particles into aluminum matrices poses significant challenges due to their limited wettability and high specific volume ratio. This research focused on developing ADC12/SiC aluminum composites with varying SiC concentrations (1.5, 2.5, and 3.5 wt%) through an innovative fabrication process. Initially, ADC12/SiC master pellets containing a high concentration of homogenously dispersed 1-μm SiC particles were produced. Subsequently, these master pellets were introduced into the molten ADC12 alloy, followed by the dispersion of SiC particles via stir casting assisted by ultrasonication. The study assessed the impact of SiC weight fractions on the microstructures, mechanical properties, and machinability of the fabricated composites. The results revealed significant microstructural improvements and a more even distribution of SiC reinforcement inside the ADC12 matrix after the application of this innovative processing method. Increased SiC concentration led to notable refinement of α-aluminum grains and eutectic Si, as well as a more uniform dispersion of intermetallic phases. Additionally, a substantial increase in tensile properties and hardness was observed with the increment of SiC content. Particularly, the ADC12/3.5 wt%SiC composite exhibited a 46.73% increase in hardness and notable enhancements in yield strength, ultimate tensile strength, and elongation, denoted as 201.7 MPa, 241.1 MPa, and 3.40%, respectively, as compared with those of the unreinforced ADC12 alloy. Moreover, the ADC12/SiC composites demonstrated reduced surface roughness compared to the unmodified ADC12 alloy, indicative of a superior surface finish. With the addition of a high SiC content, the chip morphology was observed to change from continuous to discontinuous following a turning operation.

Laser clad CoCrFeNiTixNby hypoeutectic high-entropy alloy coating: Effects of Ti and Nb content on mechanical, wear and corrosion properties

High-entropy alloys (HEAs) exhibit significant potential for advanced wear and corrosion-resistant applications. This study investigates the influence of Ti and Nb doping on the microstructure, phase composition, and properties of CoCrFeNiTixNby HEAs synthesized using high-speed laser cladding (HLC). The results demonstrate that increasing Ti and Nb content transforms the coating structure from a face-centered cubic (FCC) phase to a hybrid structure comprising FCC, body-centered cubic (BCC), and Laves phases, leading to a linear enhancement in surface hardness. The incorporation of Ti and Nb not only promotes the preferred orientation of the FCC phase (111) crystal plane but also significantly enhances tensile strength, though this comes at the expense of reduced plasticity. Specifically, the CoCrFeNiTi0.6Nb0.15 coating attains an ideal balance between strength and ductility, with a tensile strength of 1641.8 MPa and a tensile strain of 15.9 %, achieved through the formation of a eutectic structure. This coating also exhibits superior wear resistance and outstanding corrosion resistance, which are attributed to the stability of the passivation film, reinforced by the (111) crystal plane and high-density dislocations. These findings provide both theoretical and empirical foundations for the design of high-performance HEAs, underscoring their potential in industrial applications requiring robust wear and corrosion resistance.

Optimization of friction stir processing parameters to improve mechanical properties and microstructure of Al5083 aluminum alloy reinforced with AlCoCrFeNiSi high-entropy alloy

Abstract This study explores integrating AlCoCrFeNiSi high-entropy alloy (HEA) particles into the Al5083 aluminum alloy matrix via Friction Stir Processing (FSP) to enhance mechanical characteristics. Microstructural analysis reveals a homogeneous distribution and size reduction of HEA particles, contributing to improved structural strength. X-ray diffraction (XRD) examination confirms the formation of solid solution phases in the HEA particles, validating their role in enhancing material properties. Through the utilization of Design of Experiments (DOE) and Response Surface Methodology (RSM), FSP parameters are systematically optimized, enabling precise predictions of mechanical behavior. Multi-response optimization identifies the optimal combination of FSP parameters, resulting in significant enhancements in Ultimate Tensile Strength (UTS) and Hardness, reaching 314 MPa, 42% elongation, and 75 HV, respectively. Scanning Electron Microscopy (SEM) analysis of tensile test specimens elucidates the impact of varied FSP parameters on microstructural features, emphasizing the importance of optimal mixing for improving interfacial bonding and mechanical properties. This study underscores the effectiveness of integrating HEA particles and optimizing FSP parameters to elevate the mechanical properties of Al5083 aluminum alloy, paving the way for tailored composite materials with enhanced performance for specific applications.

Microstructure evolution and property enhancement of CuCr50 alloys through the synergistic effects by hot-forging deformation and heat treatment

In this study, CuCr50 alloys were prepared by aluminum thermal reduction-high frequency refining process, and the properties were improved through hot forging and heat treatment. With increasing deformation, large Cr particles were spheroidized and refined, significantly improving the performance of the alloy. When the deformation exceeds 27%, the conductivity reaches 17.73 MS/m, the hardness reaches 116.5 HB, and the density reaches 7.91 g/cm3. After solution at 975 °C for 1h and aging at 550 °C for 4h, the conductivity of the CuCr50 alloy further increased to 19.63 MS/m, the hardness reaches 121.5 HB. Compared with the as-cast alloy, the conductivity, hardness and density are increased by 71.07%, 18.81% and 2.99%, respectively. In the 5% deformed CuCr50 alloy the precipitates of nanoscale Cr particles formed a co-lattice with the copper matrix. In the 14% deformed CuCr50 alloy, nanoscale Cr particles precipitated and dispersed in the Cu matrix, and the relationship between the precipitated Cr phase and the Cu matrix was incoherent. The amount of precipitated Cr phase in the 27% deformed CuCr50 alloy had a semi-coherent relationship with the Cu matrix, the orientations of Cu(2‾00)//Cr(110). The hardness enhancement is mainly attributed to grain refinement and density increase, and the conductivity enhancement is mainly attributed to Cr particle precipitation after aging treatment.

Microstructure and mechanical properties of TiC reinforced NbC-Ni4VC4Mo2C cermets

Abstract The class of NbC-Ni cermets has emerged as a promising environmentally friendly alternative to WC-Co cemented carbide tools, although some inherent properties i.e. room temperature hardness and flexural strength, of NbC-Ni cermets may require further enhancements. To enhance the properties of NbC-Ni cermets, diverse methodologies were applied, including grain inhibition and the strengthening of the cermet through the use of reinforcements. This study systematically examined the impact of TiC additions, specifically at 10% and 20%, on both the microstructure and mechanical properties of NbC-12Ni-4VC-4Mo2C cermets. NbC-12Ni cermets were fabricated via vacuum liquid phase sintering (LPS) at 1400 °C and 1450 °C. Enhancements by incorporating 4% VC and 4% Mo2C, followed by TiC at 10% and 20% concentrations to the NbC-Ni-4VC4Mo2C cermet were made. XRD and SEM results confirm the formation of (Nb, X, Y) C solid solution cubic FCC carbides. Significant grain refinement was evident in the cermet samples, subjected to grain inhibition. The observed grain sizes ranged from a maximum of 6.84 μm (in NbC12Ni) to a minimum of 2.154 μm (in the sample containing 20% TiC) at 1450 °C. The incorporation of 20TiC at 1450 °C led to a remarkable 26.5% enhancement in average hardness compared to NbC-Ni cermet, and a 4.2% improvement over the 4VC4Mo2C cermet. At 1450 °C, 20TiC reinforcement led to an average fracture toughness of 9.331 MPa√m, representing a 4.56% improvement over the 4VC4Mo2C cermet. However, there was a marginal reduction in toughness compared to the NbC-Ni cermet. Moreover, the addition of TiC led to a decrease in the flexural strength of the cermets, with a maximum flexural strength of 939 N mm−2 recorded for NbC-Ni-4VC4Mo2C, representing an 11.6% increase compared to the NbC-Ni cermet.

Tribocorrosion in nitric acid of Zr alloy, Ti alloy, and 310 SS used for reprocessing of spent nuclear fuel

The tribocorrosion behavior of the three representative dissolver materials, namely zirconium (Zr) alloy, 310 stainless steel (SS), and titanium (Ti) alloy in HNO3 was systematically investigated by SEM, XPS, and Nanoindentation. The results revealed that Zr alloy possesses high corrosion resistance but a less favorable tribocorrosion resistance, whereas 310 SS presents a comparatively better tribocorrosion resistance but insufficient corrosion resistance. Moreover, both the coefficient of friction and wear loss of all three alloys were decreased at 0.8 V compared to −0.8 V, demonstrating an antagonistic effect of corrosion on wear, attributed to the lubrication and hardness enhancement of oxide layers. The present work offers a new perspective on the tribocorrosion behavior of continuous dissolvers used for reprocessing spent nuclear fuel.

Self-formation of dual-phase nanocomposite Zr–Cu–N coatings based on nanocrystalline ZrN and glassy ZrCu

A novel type of nanocomposite Zr–Cu–N material based on hard nanocrystalline ZrN and amorphous glassy ZrCu was prepared by atom-by-atom deposition using reactive magnetron co-sputtering. The elemental composition of the coatings was systematically controlled over a wide range, so that the stoichiometry of both phases was the same in all coatings and only phase fractions varied. Experimental results obtained using X-ray diffraction and electron microscopies were complemented by thirteen ab-initio simulations for the same coating compositions. We found that the structure of the as-deposited Zr–Cu–N coatings undergoes a gradual transition from an amorphous to nanograined and finally to nanocolumnar structure. When ZrN fraction exceeds 20 mol.%, both phases exhibit the tendency for spontaneous segregation even without heating, forming a heterogenous dual-phase nanocomposite structure. At approximately 50 mol.% ZrN, the ZrN nanocrystals enveloped by a relatively thin amorphous ZrCu phase reach an optimum size (3–5 nm), resulting in a maximum enhancement of hardness by 38 % compared to the rule of mixture. For ZrN fractions > 80 mol.%, hardness and plastic work fraction follow the trend proposed by the rule of mixture and the coatings with a lower hardness but a higher plasticity compared to the ZrN coating are prepared.

Kinetics-controlled reaction pathway and microstructure development of Ti3SiC2-TiC composite processed through reactive spark plasma sintering

Reactive spark plasma sintering of ternary Ti-Si-C system was performed using three different powder precursors systems 3Ti/Si/2C, 3Ti/SiC/C and 2Ti/TiC/Si, to explore the fundamental physics behind Ti3SiC2 MAX phase formation, its stability and microstructure development, and, finally linked with its hardening and contact induced damage tolerance. Phase evolution in Ti-Si-C system is a complex phenomenon, and, present experimental conditions never yield a phase pure Ti3SiC2 MAX phase, rather results in varying volume fractions of Ti3SiC2-(Tix,Si1-x)C solid solution due to non-equilibrium processing conditions exerted by SPS processing which restricts coherent site specific diffusional jumps and promotes the formation of (Ti, Si)C solid-solution instead of well reported non-stoichiometric TiCx. 3Ti/SiC/C precursor was the best candidate for processing composite with highest yields of Ti3SiC2. Phase evolution is guided by the free energy of formation of different phases and chemical affinity amongst the constituent elements rather than the equilibrium phase diagram of the Ti-Si-C system. Presence of free carbon, low temperature liquid phase and slow heating rate are the key requirements for forming phase pure Ti3SiC2, where excess free carbon reduces the stability of Ti3SiC2 via decarburization. Non-equilibrium processing conditions impart nano-precipitation of coherent hexagonal Ti3SiC2 precipitates within a cubic (Ti, Si)C matrix with a distinct orientation relation of (220)matrix ║(0004)precipitate and <114>matrix ║<2–1–10>precipitate that has never been reported, instead of growing highest density plane of hcp-on-fcc matrix. Coherency strain and fine interlocking microstructure of the as-processed composite experiences ≈36 % of enhancement in hardness followed by an improved contact damage for the as-processed composite.

Study of strengthening mechanisms in Al-Cu and Al-Cu-Mg systems subjected to plastic deformation and T6 treatment

ABSTRACT A series of Al-4Cu and Al-2Cu-2Mg wt.% alloys were synthesized through casting and subjected to plastic deformation to evaluate the interaction and contribution of the different strengthening mechanisms since the experimental Vickers microhardness test. The plastic deformation was performed by cold-rolling to achieve a 50% thickness reduction. The results show that solid solution strengthening is the main mechanism responsible for the total hardness enhancement of the alloys, and the Mg presents a higher hardening capacity for the solid solution strengthening than the Cu. For Al-4Cu alloy, competition between the annihilation of dislocations and the formation of precipitates generates an apparent low response precipitation hardening. Nevertheless, for Al-2Cu-2Mg alloy, the Mg addition allowed retard the dislocation annihilation induced an apparent higher response precipitation hardening.

The electromagnetic effect on microscopic features of Co-6 coatings on U71Mn by pulse current-assisted laser cladding

The hardness variation and the behavior of elemental diffusion in pulse current-assisted laser melting of multi-pass monolayer coatings and HAZ were investigated. The results showed that the coating microstructure grains were refined when the pulse current intensity increased from 5A to 10A. The electromagnetic effect generated by the pulse current drove the Fe element in the matrix to diffuse into the coating. When the pulse current was increased to 20 A, the electromagnetic impact effect overcame the bonding strength between the molten pool metals, which caused the coating to transcrystalline repture in the direction of the current movement. Meanwhile, when the pulse current increased within limits, the reduction of grain size and Fe diffusion resulted in more than two-fold hardness enhancement of the coating and HAZ.

Atomic-scale investigation of the synergistic impact of Mo and Nb addition on enhancing the performance of laser cladding FeCoCrNi-based high entropy alloy coatings

Utilizing synchronous powder feeding laser cladding technology, two high entropy alloy coatings, FeCoCrNiMo and FeCoCrNiMoNb, were deposited on the surface of low-carbon steel. An in-depth investigation into the synergistic interplay of Mo and Nb on FeCoCrNi-based high entropy alloy coatings was conducted. The findings reveal that FeCoCrNiMo comprises an FCC stable solid solution, Mo3Co3C, and Ni3Mo3C. Conversely, FeCoCrNiMoNb exhibits a composition comprising an FCC stable solid solution phase, NbC, and (Mo, Nb)C. This is attributed to the robust interaction between Mo and Nb, wherein Mo infiltrates the NbC lattice, substituting for a portion of Nb atoms. Notably, the synergistic influence of Mo diminishes the formation energy of NbC, thereby lessening the energy barrier encountered during the nucleation of (Mo, Nb)C. Consequently, the incorporation of Mo facilitates the precipitation of Nb. The refined microstructure and solid solution strengthening effect of (Nb, Mo)C and NbC, coupled with their elevated Vickers hardness and hard elastic ratio, contribute significantly to the notable enhancement in surface hardness and wear resistance observed in the FeCoCrNiMoNb high entropy alloy coating.

Circular Economy of Construction and Demolition Waste for Nanocomposite Cement: XRD, NMR, Vickers, Voltammetric and EIS Characterization.

In this paper, we present the structural, mechanical and electrical properties of composite cement materials that can be widely used as substituent for cement. We start with the characterization of a composite cement sample using an analysis of X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectra. The measurements of the Vickers hardness, cyclic and sweep linear voltammetry and electrochemical impedance spectroscopy (EIS) of composite cement materials were also recorded. This study compared the effect of the different nanocomposites added to cement on the mitigation of the alkali-silica reaction, which is responsible for the swelling, cracking and deleterious behavior of the material. The enhancement in Vickers hardness was more pronounced for composite cement materials. In contrast, the values of Vickers hardness decreased for the composite cement containing mortar and the control sample, suggesting that the long-term performance of cement was compromised. In order to obtain information about the bulk resistance of the composite cement material, electrochemical impedance spectroscopy (EIS) data were employed. The results suggest that for composite cement materials, there is an improvement in bulk electrical resistance, which can be attributed to the lower amounts of cracks and swelling due to lower expansion. In the control sample, a reduction in the bulk resistance suggests the formation of microcracks, which cause the aging and degradation of the material. The intersection of arcs in the EIS spectrum of the mixed composite cement sample gradually increased by an alkaline exposure of up to 21 days and finally shifted towards a low value of high frequency with an increase in alkaline exposure of up to 28 days.

Experimental investigation on microstructure, mechanical and optical properties of RB-SiC ablated by nanosecond pulsed laser in nitrogen atmosphere

Reaction-bonded silicon carbide (RB-SiC) has gained significant attention owing to its exceptional physical and chemical properties. Improving the photovoltaic efficiency and mechanical properties of RB-SiC is conducive to further enhancing its applicability. Laser gas nitriding is an effective strategy to simultaneously reduce the surface reflectivity and enhance the surface hardness of materials. Accordingly, the evolution of microstructure, mechanical and optical properties of RB-SiC composite ablated by nanosecond pulsed laser in nitrogen atmosphere was comprehensively investigated. After laser gas nitriding, the surface hardness of RB-SiC composite was increased by 10.6–44.6 %. The chemical composition analysis indicated that Si-based nitride was formed on the laser-ablated surface, which was mainly responsible for the hardness enhancement. Additionally, the reflectivity of the laser-ablated surface was reduced by up to 95.2 % compared to the original RB-SiC composite. This study provides a straightforward and effective method to simultaneously improve the mechanical and optical properties of RB-SiC composites.

Assembly behavior and nano-scale microstructure of tamarind gum/xanthan synergistic interaction gels

Synergistic interaction gels (SIGs) hold immense promise for applications in 3D printing, colonic drug delivery, and sustained release. The amalgamation of xanthan and tamarind gum (TMG) gives rise to SIGs through molecular interaction; however, the intricacies of their assembly behaviors remain elusive. This work elucidates that in xanthan-rich systems, the predominant formation of xanthan aggregations shapes network assembly structure, with TMG clusters adhering to them. Conversely, in TMG-rich systems, TMG clusters actively participate in creating a “sea-island” assembly structure enveloped by xanthan aggregations. Higher concentration of TMG contributes to augmenting the association extent of TMG and xanthan. The heightened binding between TMG and xanthan correlates with an increase in chain distance in scatters and the compactness of scatter arrangement. These favor the development of micro-structures with a relatively larger mesh size and the enhancement of gel hardness. This study serves to facilitate the design and production of SIGs-based artificial gel foods with the requisite performance characteristics, such as artificial sea cucumber and porcine back fat.

Unraveling Lattice-Distortion Hardening Mechanisms in High-Entropy Carbides.

Uncovering the hardening mechanisms is of great importance to accelerate the design of superhard high-entropy carbides (HECs). Herein, the hardening mechanisms of HECs by a combination of experiments and first-principles calculations are systematically explored. The equiatomic single-phase 4- to 8-cation HECs (4-8HECs) are successfully fabricated by the two-step approach involving ultrafast high-temperature synthesis and hot-press sintering techniques. The as-fabricated 4-8HEC samples possess fully dense microstructures (relative densities of up to ≈99%), similar grain sizes, clean grain boundaries, and uniform compositions. With the elimination of these morphological properties, the monotonic enhancement of Vickers hardness and nanohardness of the as-fabricated 4-8HEC samples is found to be driven by the aggravation of lattice distortion. Further studies show no evident association between the enhanced hardness of the as-fabricated 4-8HEC samples and other potential indicators, including bond strength, valence electron concentration, electronegativity mismatch, and metallic states. The work unveils the underlying hardening mechanisms of HECs and offers an effective strategy for designing superhard HECs.

Enhanced tribological behavior and corrosion resistance in AlSiC-based coatings through varied carbon content

A series of AlSiC-based nanocomposite coatings with varying carbon concentrations were fabricated by filtered cathodic vacuum arc (FCVA) technology. These coatings featured an amorphous matrix with embedded Al4Si3C6 nanocrystals. With the increase in carbon content, the proportion of amorphous structure within the structure grew, which was accompanied by a rise in sp3 hybridized carbon bonds. This compositional change led to a significant enhancement in hardness and toughness. Notably, the AlSiC coating deposited at a flow rate of 50 sccm displayed exceptional mechanical properties, including a high hardness of approximately 23.2 GPa, toughness indices of H/E = 0.096 and H3/E2 = 0.216 GPa, a low friction coefficient around 0.18, a wear rate as low as ∼1.09 × 10−5 mm3 N−1 m−1, and a corrosion current density of approximately 1.08 × 10−9 A/cm2. The coating's superior tribological characteristics and corrosion resistance can be attributed to two main factors. The enhanced hardness and toughness indices (H/E and H3/E2) contributed to its improved deformability, which is essential for wear resistance. Secondly, the presence of a graphite layer formed during friction provided self-lubrication, further reducing wear. Additionally, the chemical inertness of both the amorphous SiC and the amorphous carbon phases within the nanocomposite structure significantly bolstered the coating's resistance to corrosion. The AlSiC nanocomposite coatings deposited by FCVA exhibit outstanding mechanical properties, tribological performance, and corrosion resistance, making them highly suitable for applications in environments where wear and corrosion are significant concerns.

Design, preparation, and enhanced mechanical properties of novel plate-like grains toughened (Zr, Ti, W, Ta)C medium-entropy ceramics fabricated by in-situ reaction hot-pressing

Novel plate-like (Ti, Zr)B2 toughened (Zr, Ti, W, Ta)C medium-entropy ceramics were designed based on the atomic scale, nanoscale, and microscale, and prepared via the in-situ reaction hot-pressing adopting (Ti, W, Ta)C and ZrB2 powders. The multiphase ceramics were primarily composed of the (Zr, Ti, W, Ta)C matrix and plate-like (Ti, Zr)B2. When the addition of ZrB2 exceeds 50 mol%, the residual ZrB2 causes the secondary primary phase to change from (Ti, Zr)B2 to (Zr, Ti)B2. The improvement of fracture toughness is primarily influenced by the plate-like (Ti, Zr)B2 on crack propagation mechanisms such as bridging effect and crack deflection. (Ti, W, Ta)C- 50 mol% ZrB2 (raw powder composition) exhibits outstanding mechanical properties, boasting a Vickers hardness of 24.9 GPa, fracture toughness of 5.5 MPa·m1/2, and flexural strength of 552 MPa, which present a novel avenue for achieving a synergistic enhancement in Vickers hardness and fracture toughness within medium-entropy carbide ceramics.

Influence of the Nb–Al ratio on homogenization behavior and hierarchical microstructures in high-entropy superalloys

In this investigation, we explore the impact of the Nb–Al ratio on the microstructural and mechanical properties of high-entropy superalloys (HESAs), focusing on hierarchical microstructures. Utilizing a series of HESAs with varying Nb–Al ratios, our study employs advanced characterization techniques, including differential scanning calorimetry (DSC) for thermal analysis, electron probe micro-analyzer (EPMA) for compositional analysis for the design of a homogenization treatment at 1500 K/24 h. Transmission electron microscopy (TEM) reveals that the increasing Nb–Al ratio refines the γ' precipitates and influences the size and volume fraction of embedded hierarchical γ particles. ThermoCalc equilibrium phase analysis and Vegard's-law calculations reveal a minimal lattice misfit between these phases, highlighting the interplay between Nb–Al ratio and phase stability. The increasing Nb–Al ratio inhibits the formation of hierarchical γ particles. We observe an enhancement in hardness from 433 HV to 492 HV with an increasing Nb–Al ratio. This study provides valuable insights into the role of Nb and the Nb–Al ratio in HESAs with hierarchical microstructures, demonstrating its significant influence on γ particle formation within γ' precipitates and mechanical strength. The findings advance our understanding of alloy design and pave the way for developing advanced HESAs for high-temperature applications.

Microstructural evolution and phase analysis of SS410–Al2O3–SiC multilayered functionally graded composite fabricated through laser cladding

In the present study, a functionally graded metal-ceramic composite structure comprising SS410, Al2O3, and SiC particles with varying composition, structure and properties in a single deposit was successfully fabricated using direct energy deposition (DED). The composition varied from 90 % SS410 with 10 % (xAl2O3 + ySiC) to 10 % SS410 with 90 % (xAl2O3 + ySiC), where x = 70 % and y = 30 % in a five-layered FGM design. The microstructure, phase evolution and mechanical properties of the components with different composition gradients were characterized by microscopy, energy dispersive spectroscopy, wavelength dispersive spectroscopy, X-ray diffraction and micro hardness. The investigation revealed that complex phases such as C0.12Fe0.79Si0.09, M7C3, Fe3C, and Fe3Si formed as a result of the interaction between SiC and SS410 during the cladding process. Microstructural analysis showed a transition from columnar dendrites at the bottom zone of the cladding to a typical cellular structure and carbide particle agglomerates in the middle zone, with finer grains at the top zone. This gradation in microstructure correlated with an increase in microhardness ranging from 299 HV at the bottom to 966 HV at the top. This enhancement in hardness is primarily attributed to solid solution strengthening from C and Si originating from the decomposition of SiC and the precipitation of intermetallic phases.