EFFECT OF WETTING AGENT AND CARBIDE VOLUME FRACTION ON THE WEAR RESPONSE OF ALUMINUM MATRIX COMPOSITES REINFORCED BY WC NANOPARTICLES AND ALUMINIDE PARTICLES

Aluminum matrix composites were prepared by adding submicron sized WC particles into a melt of Al 1050 under mechanical stirring, with the scope to determine: (a) the most appropriate salt flux amongst KBF4 , K2 TiF6 , K3 AlF6 and Na3 AlF6 for optimum particle wetting and distribution and (b) the maximum carbide volume fraction (CVF) for optimum response to sliding wear. The nature of the wetting agent notably affected particle incorporation, with K2 TiF6 providing the greatest particle insertion. A uniform aluminide (in-situ) and WC (ex-situ) particle distribution was attained. Two different sliding wear mechanisms were identified for low CVFs (≤1.5%), and high CVFs (2.0%), depending on the extent of particle agglomeration

Pulsed plasma deposition of Fe-C-Cr-W coating on high-Cr-cast iron: Effect of layered morphology and heat treatment on the microstructure and hardness

Pulsed plasma treatment was applied for surface modification and laminated coating deposition on 14.5 wt%-Cr cast iron. The scopes of the research were: (a) to obtain a microstructure gradient, (b) to study the relationship between cathode material and coating layer microstructure/hardness, and (c) to improve coating quality by applying post-deposition heat treatment. An electrothermal axial plasma accelerator with a gas-dynamic working regime was used as plasma source (4.0 kV, 10 kA). The layered structure was obtained by alternation of the cathode material (T1 - 18 wt% W high speed steel and 28 wt% Cr-cast iron). It was found that pulsed plasma treatment led to substrate sub-surface modification by the formation of an 11–18 μm thick remelted layer with very fine carbide particles that provided a smooth transition from the substrate into the coating (80–120 μm thick). The as-deposited coating of 500–655 HV0.05 hardness consisted of “martensite/austenite” layers which alternated with heat-affected layers (layers the microstructure of which was affected by the subsequent plasma pulses). Post-deposition heat treatment (isothermal holding at 950 °C for 2 h followed by oil quenching) resulted in precipitation of carbides M7C3, M3C2, M3C (in Cr-rich layers) and M6C, M2C (in W-rich layers). These carbides were found to be Cr/W depleted in favor of Fe. The carbide precipitation led to a substantial increase in the coating hardness to 1240–1445 HV0.05. The volume fraction of carbides in the coating notably increased relatively to the electrode materials

Microstructure And Mechanical Properties Of Al-WC Composites

The scope of the research work is the production and characterization of Al matrix composites reinforced with WC ceramic nanoparticles. The synthesis process was powder metallurgy. The produced composites were examined as far as their microstructure and mechanical properties (resistance to wear, micro/macrohardness). Intermetallic phases (Al12W and Al2Cu) were identified in the microstrucutre. Al4C3 was not detected in the composites. Adding more than 5 wt% WC to the aluminum, microhardness and wear resistance exceed the values of Al alloy. Composites having weak interface bond performed the highest wear rate

(FeMnNi)84(AlTi)16 high‑entropy alloy: correlation of microstructure, strengthening mechanisms and hardness at various conditions (As‑Cast, solution treated, aged)

A (FeMnNi)84(AlTi)16 high-entropy alloy was produced by vacuum arc melting successfully. The microstructure of the as-cast state showed the existence of two FCC phases along with potential precipitates. The solution treatment response of the alloy for 2 h at 1150 °C and the effect of aging time at 750 °C in the microstructure and microhardness were also evaluated. It was observed that the solution treatment parameters were insufficiently low to dissolve the as-cast precipitates into the matrix. The double FCC matrix identified may be correlated with a solidification range and insufficient diffusion during the solidification process. The maximum hardness at 90 min aging time can be mainly attributed to the precipitation shearing mechanism in both matrix areas. The lower hardness value reported at 160 h aging time was estimated that it is derived by the change of the main strengthening mechanism from shearing to Orowan. The island-like precipitates that depleted Ti element from the Ni-rich intergranular area may be identified as a Ni2AlTi Heusler phase

A New Cooling-Rate-Dependent Machine Learning Feature for the Design of Thermally Sprayed High-Entropy Alloys

Highly accurate machine learning (ML) approaches rely heavily on the quality of data and the design features that are used as inputs to the model. The applicability of these methods for phase formation predictions is questionable when it comes to the design of thermally sprayed high-entropy alloy (HEA) coatings using gas or water atomized powders as feedstock material. Phase formation from liquid state depends on the cooling rate during atomization which is several orders of magnitude higher when compared to arc-melted as-cast HEAs. In addition, during plasma spray the powder melts in the flame and re-solidifies under different cooling rates during deposition. To our knowledge, almost all ML algorithms are based on available datasets constructed from relatively low cooling rate processes such as arc melting and suction casting. A new approach is needed to broaden the applicability of ML algorithms to rapid solidification manufacturing processes similar to gas and water atomization by making use of existing data and theoretical models. In this study the authors introduce a cooling-rate-dependent design feature that can lead to accurate predictions of the HEA powder phase formation and the subsequent phases found in the spray coated materials. The model is validated experimentally and also by comparing the predictions with existing coating related data in the literature

Al-RHEA Particulates MMCs by PM Route: Mechanical Properties and Sliding Wear Response

New particle reinforced aluminum matrix composites with the addition of refractory High Entropy Alloy, MoTaNbVW, fabricated via powder metallurgy process were assessed for their properties. Basic mechanical properties (modulus of elasticity, hardness) for the aluminum matrix, the pure aluminum and the reinforcement phase were assessed by means of dynamic nano-indentation technique. Nano-indentation based creep response was also evaluated in these three areas of interest. Hardness shows an increase with the addition of the particulates and so does the elastic moduli and the ratio of the energy absorbed in the elastic region. The creep response was approached in terms of dislocation mobility and critical volume for their nucleation. The produced Al–HEA composites were also studied for their sliding wear behavior and showed that with the increase in percentage of RHEA particulates the wear resistance increases. Microstructural considerations, wear track morphologies, and debris characteristics were used for the assessment of the involved wear mechanisms

Al-RHEA Particulates MMCs by PM Route: Mechanical Properties and Sliding Wear Response

New particle reinforced aluminum matrix composites with the addition of refractory High Entropy Alloy, MoTaNbVW, fabricated via powder metallurgy process were assessed for their properties. Basic mechanical properties (modulus of elasticity, hardness) for the aluminum matrix, the pure aluminum and the reinforcement phase were assessed by means of dynamic nano-indentation technique. Nano-indentation based creep response was also evaluated in these three areas of interest. Hardness shows an increase with the addition of the particulates and so does the elastic moduli and the ratio of the energy absorbed in the elastic region. The creep response was approached in terms of dislocation mobility and critical volume for their nucleation. The produced Al–HEA composites were also studied for their sliding wear behavior and showed that with the increase in percentage of RHEA particulates the wear resistance increases. Microstructural considerations, wear track morphologies, and debris characteristics were used for the assessment of the involved wear mechanisms