Macro Hardness Research Articles

Expounding the application of nano and micro silica as a complementary additive in metakaolin phosphate geopolymer for ceramic applications—micro and nanoscale structural investigation

Metakaolin phosphate geopolymers comprising poly-phospho-siloxo units are known for their structural performance, additionally advancing their microstructure with the transformation of crystalline berlinite phases at elevated temperatures. The intrinsic reaction of Al of metakaolin in the acid exploited, but the reaction of secondary silica phases is limitedly known. Metakaolin as a primary precursor (M) with the addition of 2% and 5% of nano silica (MS2 and MS5) and micro silica (MM2 and MM5) cast using 8-M phosphoric acid was cured at 80 °C. To enhance the utilization of geopolymer in any high-temperature applications, the structural transformations were studied after heating to various temperatures (200, 400, 600 and 800 °C) by XRD, Raman, TGA-DTA, SEM, XPS, FTIR and MAS-NMR. Sample M attained a strength of 46.2 MPa enhanced to 63.6 MPa in MS5 and 54.2 MPa in MM5. This can be ascribed from the transformation of Si–O–Al–O–Si into Si–O–Al–O–P from Raman bands. Comparing the chemical shift of Al (IV) to control, micro silica addition shifts the signal to a lower field (53 to 50 ppm) related to the increase of the number of Al-connected Si to give a tougher network. Nanoindentation is visualized from hardness and elasticity, and the corresponding values are 1.4 to 2.1 GPa and 0.8 to 1.4 GPa for loads ranging from 20 to 100 mN in silica-reinforced samples that are much higher than M. The micro and macro hardness is due to the reinforcement of quartz in micro silica around the gel. TGA-DTA showed that the reduction of mass loss is as high as 25.4% in control whereas 17.2% in MS5 and 15.8% in the MM5. Further, shrinkage rate in MS5 and MM5 was as low as − 1.1% and − 0.8% throughout the temperature range from 25 to 1000 °C and thus provides the way of use of nano and micro form of silica for better thermal resistance.Graphical

Comprehensive analysis of mechanical properties, wear, and corrosion behavior of AA7075-T6 alloy subjected to cryogenic treatment for aviation and defense applications

It is important that the parts to be used in the aviation and defense industry have high wear, fatigue and corrosion resistance. AA7075-T6 alloys are increasingly used in every field due to their advantageous physical and mechanical properties. However, some of the materials of this alloy types exhibit excellent fatigue strength and ductility, but their surface hardness and surface roughness after processing may be poor. For this reason, the wear resistance of AA7075-T6 aluminum alloy expected to be improved in order to increase their corrosion resistance properties. In this work, cryogenic treatment was applied to AA7075-T6 alloy and the mechanical characteristics, wear and corrosion behaviors of these samples were examined. As a result of the experiments, it was determined that cryogenic treatment improved the wear behavior of AA7075-T6 alloy. The untreated sample was found to have the highest wear rate, whereas the sample with deep cryogenic treatment (DCT) had the lowest wear rate. The hardness of the DCT process increased by 5.79 %, according to macro hardness measurements, making the AA7075-T6 alloy harder from 80.16 HRB to 84.8. The SEM images revealed that, the shallow cryogenic and deep cryogenic operations had substantial effects on the microstructure by modifying the size and distribution of precipitates in the AA7075-T6 alloy. In addition, tensile and hardness tests were carried out to assess the mechanical characteristics of the samples. Accordingly, the maximum tensile strength and hardness values were obtained in the deep cryogenically treated sample. The tensile strength of the DCT sample was approximately 544.18 MPa, a considerable 11.5 % increase above the untreated sample's 488.07 MPa strength. In potentiodynamic polarization testing, the DCT treated sample was determined to have the maximum corrosion resistance. Among the materials tested, the DCT sample showed the strongest corrosion resistance, with a corrosion potential of −0.689 V and a corrosion rate of 0.021 mm/year. Wear rate analysis revealed that DCT samples experienced the least material loss, demonstrating improved abrasion resistance. Enhanced hardness and the formation of stable oxide tribo-layers contributed to these superior wear characteristic.

Correlated high throughput nanoindentation mapping and microstructural characterization of wire and arc additively manufactured 2205 duplex stainless steel

Duplex stainless steels (DSS) in wire and arc additive manufacturing (WAAM) have attracted significant research attention due to their mechanical properties and corrosion resistance. This study uses conventional and nanomechanical testing methods to compare the mechanical and microstructural behaviors at macroscopic and microscopic length scales. Macro hardness (HV10) testing yielded 259 and 249 in low and high heat input (HI) samples, respectively, while ferrite content averaged 52.7 and 48.5%. However, these results fail to provide conclusive insight into the potential influence of microstructural variations at the macroscopic level, likely due to the composite response of the material. To overcome this limitation, the mechanical response of the DSS samples is assessed at the grain level via high throughput nanoindentation mapping with image processing to track the location of each indent. This approach enabled differentiating the indents landing on ferrite and austenite phases as well as those landing on the interfaces. The results showed that the austenite phase had higher hardness (4.30 and 4.35 GPa) than the ferrite phase (3.89 GPa and 4.03 GPa) for high and low HI samples, respectively. The observed differences in hardness between the phases can be attributed to higher nitrogen content in the austenitic phase.

Improving mechanical properties of W-Ni3Al alloy through Zr element addition: Solid-solution and oxide particle strengthening

In this study, fine Ni3Al flakes facilitated the W-Ni3Al alloy liquid phase sintering, while the added 0.9 wt% Zr element enhanced its mechanical properties, finally obtaining the 1200 °C sintered W-Ni3Al-Zr alloy (WNZ-1200 alloy) with excellent comprehensive properties. Specifically, the relative density, tungsten grain size, bending strength, and macro hardness of WNZ-1200 alloy were 98.26 ± 0.31 %, 3.06 ± 0.65 µm, 1472.56 ± 61.90 MPa, and 76.10 ± 0.82 HRA, respectively. By analyzing the alloy’s phase and microstructure, its excellent mechanical properties were originated from the formed Ni3(Al, W, Zr) solid solution, unique nano-Al2O3 ‘rivet’, the semi-coherent interface of W/t-ZrO2, oxide dispersion strengthening, and the t-ZrO2 phase transformation strengthening.

Developing austenitic high-manganese high-carbon steels for biodegradable stent applications: Microstructural and mechanical studies

Fully degradable stents that temporarily support healing tissue can solve potential long-term complications associated with permanent implants. In this study, we investigate austenitic high-manganese high-carbon steels as promising candidates for such biodegradable stent applications. The microstructural characteristics and mechanical properties of the Fe–Mn–C steels were systematically analysed to assess their suitability for this purpose. A series of four austenitic Fe–Mn–C steels with varying manganese (15 and 30 wt%) and carbon (0.6–1.0 wt%) content were processed by vacuum induction casting, annealing and hot forging. Microstructural analysis was performed, and the hot forged materials were further evaluated using ultrasound, macro hardness, and (stopped) quasi-static tensile tests to assess stent-related parameters. In contrast to the as-cast state, the hot forged steels exhibited high chemical homogeneity, as was found by energy-dispersive X-ray spectroscopy (EDXS). Electron backscatter diffraction (EBSD) revealed comparability between the four steels regarding their annealing twin fractions and grain size distributions. An austenitic microstructure was revealed for all modifications by transmission X-ray diffraction (XRD), except Fe–15Mn–0.6C, which displayed a minor ε–martensite fraction. Reducing manganese from 30 to 15 wt% resulted in favourable effects, including a higher Young's modulus, lowered offset yield strength, and an increased ultimate tensile strength due to larger strain hardening while preserving a high total elongation. However, reducing the carbon content to 0.6 wt% diminished the mechanical performance due to reduced solid solution strengthening and the ε–martensite formation. Among the investigated steels, the novel Fe–15Mn–0.8C alloy exhibited the most attractive combination of the studied properties for potential stent applications.

Mechanical Characterization and Microstructural Analysis of Stir-Cast Aluminum Matrix Composites (LM5/ZrO2)

Aluminum matrix composites (AMCs) are largely used in defense, maritime, and space applications for their excellent properties. LM5 is used where very high resistance to corrosion from seawater or marine atmospheres is required, for equipment used for the manufacture of foodstuffs, cooking utensils, and chemical plants. Zirconia is preferred over other reinforcements as it shows comparatively great refractory properties, high scratch resistance, and thermal shock resistance. Utilizing the stir casting technique, an attempt was made to produce AMCs of LM5 aluminum alloy strengthened with ZrO2. The weight percentage of ZrO2 was changed to 0%, 3%, 6%, and 9%. The specimens were prepared and tested as per ASTM standards to find the density, micro and macro hardness, impact, tensile, and compressive strength. The micrographs and SEM images confirm the uniform distribution of ZrO2 particles in the aluminum matrix. LM5/9%ZrO2 AMC has the highest density value of 2.83 g/cm3 and LM5/3%ZrO2 has the least porosity of 2.55%. LM5/9% ZrO2 has the highest hardness values of 78 VHN and 72 HRE. LM5/6% ZrO2 AMC has the highest tensile strength of 220 MPa, compressive strength of 296 MPa, and toughness of 12 J. LM5/6% ZrO2 AMCs may be used for many structural applications.

Physical Properties of the Function and Number of Empirical Macrohardness of the Material: Universal Physical Unit of Measurement of Macro Hardness (Part 2)

Physical Properties of the Function and Number of Empirical Macrohardness of the Material: Universal Physical Unit of Measurement of Macro Hardness (Part 2)

Enhanced mechanical and wear properties of aluminium-based composites reinforced with a unique blend of granite particles and boron carbide for sustainable material recycling

In this study, a two-step stir casting technique was employed to fabricate composites using scrap aluminium cans (SAC) as matrix and a unique blend of Granite Particles (GP) and boron carbide (B4C) as reinforcements. Mono and hybrid composites were developed to evaluate the effects of the GP-B4C on the microstructure, mechanical properties, wear characteristics, and fracture behaviour of the composites. The microstructural characterization of the composites revealed that the incorporation of reinforcement into the aluminium matrix led to a refined grain structure with distinct interfaces. Both mono and hybrid composites exhibited improved hardness, with the hybrid composite showing a significant increase of 15.74 % in macro hardness and 16.33 % in microhardness compared to the base material. The mono composite demonstrates the highest ultimate tensile strength of 218 MPa, followed by the hybrid composite with a strength of 192 MPa. The improved mechanical properties of the mono composite are attributed to the reduction in grain size and the enhanced interfacial bonding between the reinforcement and the matrix. Although the hybrid composite exhibited more porosities, it shows the maximum ultimate compressive strength of 1124 MPa. The tensile fractured surfaces displayed dimples, cleavage facets, transgranular cracks, and river line markings. The wear loss of the mono composite decreased by 11.2 %, while that of the hybrid composite decreased by an impressive 28 % compared to their parent base matrix. The worn surface exhibits a combination of abrasive, adhesive, and delamination wear mechanisms.

Microstructural properties and impact behavior of AA5083/Al2O3 functionally graded composite material with surface foam layer produced through powder metallurgy

The development of technology requires new generation materials that can hold different concentrations together, unlike conventional composite materials that are only reinforced. Functionally graded composite materials (FGCMs) are open to development because they are lightweight and hold concentrations with different mechanical properties. For this reason, in this study, a new generation FGCMs and aluminum foam material were combined. A new generation of functionally graded composite foam materials (FGCFMs) consisting of AA5083 alloy aluminum foam on one surface and AA5083 matrix on the other surface, and a graded composite structure with Al2O3 contents varying from 10% to 20%, 30%, 40%, 50%, and 60% were produced. AA5083, Al2O3 and TiH2 powders were weighed on a precision scale and mixed in a three-dimensional mixer for 1 h. The mixed powders were compressed under 300 MPa pressure at 500 °C and to obtain block samples of different step thicknesses (2, 4, and 6 mm). The foamable preform materials were foamed at 750 °C for about 10 min. The highest value of macro hardness value was obtained with 167 HB in the sample with a step thickness of 2 mm. In samples with step thicknesses of 4 and 6 mm, puncture did not occur at an impact energy of 300 J.

Properties and Microstructure Evaluation in NiAl-xWC (x = 0 − 90 wt.%) Intermetallic-Based Composites Prepared by Mechanical Alloying

In this work, NiAl-xWC (x = 0 - 90 wt.% WC) intermetallic-based composites were successfully synthesized by mechanical alloying (MA) and a hot-pressing approach. As initial powders, a mixture of nickel, aluminum and tungsten carbide was used. The phase changes in analyzed systems after mechanical alloying and hot pressing were evaluated by an X-ray diffraction method. Scanning electron microscopy and hardness test examination were used for evaluating microstructure and properties for all fabricated systems from the initial powder to the final sinter stage. The basic sinter properties were evaluated to estimate their relative densities. Synthesized and fabricated NiAl-xWC composites showed an interesting relationship between the structure of the constituting phases, analyzed by planimetric and structural methods and sintering temperature. The analyzed relationship proves that the structural order reconstructed by sintering strongly depends on the initial formulation and its decomposition after MA processing. The results confirm that it is possible to obtain an intermetallic NiAl phase after 10 h of MA. For processed powder mixtures, the results showed that increased WC content intensifies fragmentation and structural disintegration. The final structure of the sinters fabricated in lower (800 °C) and higher temperature regimes (1100 °C), consisted of recrystallized NiAl and WC phases. The macro hardness of sinters obtained at 1100 °C increased from 409 HV (NiAl) to 1800 HV (NiAl + 90% WC). Obtained results reveal a new applicable perspective in the field of intermetallic-based composites and remain highly anticipated for possible application in severe-wear or high-temperature conditions.

Diamond particles-reinforced Ni-based composite coating on Ti6Al4V alloy: Microstructure, mechanical, dynamic impact and dry-sliding tribological properties

Diamond particles-reinforced Ni-based composite coating was fabricated on Ti6Al4V by vacuum cladding. The microstructure, phase composition, hardness, dynamic impact and dry-sliding tribological properties of the coating have been investigated systematically. The results demonstrate that the coating consists of a tough TixNiy/Ti3Al matrix filled with hard phases of TiC, Ti3SiC2 and TiC/CrxCy covered diamond. Benefiting from the high-temperature diffusion, the coating is well-metallurgically bonded with the substrate. Compared with the Ti6Al4V substrate, the overall macro hardness (H) and nanoindentation hardness (HIT) of Ni-based composite coating increase by 1.2 times and 3.5 times, respectively. The coating has a complete residual indentation under the high frequency of impact. Its diameter and depth are 90 % and 86 % of the substrate, respectively, indicating that the coating has relatively excellent impact toughness. Further, the coating has good wear resistance under high load. Its wear rate is 7.79 × 10−5 mm3/Nm, which is only 1/6 of the Ti6Al4V substrate. Therefore, the coating has good comprehensive performance and potential practical applications.

Development of nickel alloy based hardfacing procedure for fast breeder test reactor control rod sheath using conventional gas tungsten arc welding process and metal cored alloy grade ERC Ni Cr – B

Fast Breeder Nuclear Reactors (FBR) will play a vital role to fulfill the power scarcity of developing India. The main products of the reactor assembly are manufactured using austenitic stainless steel - nuclear grades of AISI 316L. This material has excellent resistance to corrosion, better creep strength at higher temperature, and resistance to impact. Few reactor components are designed to perform rotation and translation movement for operation and control of reactor power. The relative motion between the components may lead to wear. Also, there is a possibility of self welding of these components due to high temperature and presence under a hot sodium working environment. Control rod sheath houses the control rod in a nuclear reactor which is used for raising or lowering the reactor output power. During operation of a nuclear reactor the control rod will move in and out. Due to this movement the control rod sheath will experience wear and tear. To reduce the wear and self welding problems throughout the operating period of the reactor, the components are designed with a layer of hard faced metal. Nickel based hard facing alloy is widely used for hard face coating in the nuclear reactor components. Since, it has high wear resistance under elevated temperature in the nuclear reactor. The process is done using Gas Tungsten Arc Welding (GTAW) by using the metal cored filler wire of grade ERC Ni Cr-B. Efforts have been put through this project for developing GTAW hard facing procedure and to observe the micro structure including micro hardness, macro hardness on coating as well as fusion zone and base metal.

Influence of micro boron carbide particles on microstructure, mechanical properties, and dry sliding wear strength of an aluminium Al2214-B4Cp metal matrix composite

In this experimental research, an attempt is made to develop Al2214-B4Cp composite materials with reinforcement of micro boron carbide (B4Cp) (viz. 0, 1.5, 3, 4.5, and 6 wt.%) by using a novel liquid metallurgical stir casting technique with modified bottom pouring facilities and studying the microstructure, physical, mechanical, and dry sliding wear resistance responses. The microstructure of Al2214-B4Cp composite samples with varied boron carbide weight percentages was examined under an electronic scanning microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDX) device. The physical characteristics like density and porosity, mechanical strength, such as micro and macro hardness, yield and ultimate tensile strength, and sliding wear response were examined under variable experimental conditions. The experimental results of the Al2214-B4Cp composite revealed a decreased specific density with an increased weight percentage of boron carbide (B4Cp) particulate in the matrix and a homogeneous distribution of reinforced micro boron carbide (B4Cp) particles in the Al2214 matrix. There was an appreciable improvement in mechanical properties and wear strength in composite materials as compared to an unreinforced aluminium alloy.

Development of modeling to investigate polyurethane pad hardness in chemical mechanical planarization/polishing (CMP) process

In chemical mechanical polishing (CMP) for IC fabrication, porous pads are critical for achieving extremely consistent throughput in CMP process. The pad hardness, porosity of pad, and pore sizes in the thermoplastic polyurethanes foam fabrication procedure determine the properties of CMP pads. This paper aims to develop a methodology for modeling macro and micro pad hardness. The IC1000 CMP pad has been analyzed with a developed image processing method to determine porosity and pores size. In addition, nano-indentation tests are used to determine physical properties of micro-solid components. For macro hardness analysis, five different sizes of three-dimensional representative volume elements (RVE) have been investigated using the random sequential adsorption technique. Furthermore, simulation of macro pad hardness of RVE models are completed with finite element method. Results of this study not only achieves macro hardness of CMP pad simulation as 3% errors as compared with developed micro-indentation test, but also complete three dimensional porous pad modeling with RVE.

The effect of porosity on the mechanical properties of Ti–8Nb–8Zr–8Cu alloy

The present study investigated the mechanical performance of Ti–8Nb–8Zr–8Cu (at.-%) alloys containing different porosity levels. Metallographic examination and phase analysis of samples was performed by scanning electron microscope (SEM), optical microscopy (OM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) measurements. The mechanical properties were detected by uniaxial compression test, micro and macro hardness measurements. The wear behaviour was determined by a dry wear test on the bulk sample. The ultimate compressive strength decreased from 1077.30 to 344.65 MPa with 50% porosity and the modulus of elasticity from 15.6 to 9.5 GPa. These values show that it may be suitable for bone replacement considering the stress shield effect.

An Approach to Assessing S960QL Steel Welded Joints Using EBW and GMAW

In recent years, ultra-high-strength structural (UHSS) steel in quenched and tempered (Q+T) conditions, for example, S960QL has been found in wider application areas such as structures, cranes, and trucks due to its extraordinary material properties and acceptable weldability. The motivation of the study is to investigate the unique capabilities of electron beam welding (EBW) compared to conventional gas metal arc welding (GMAW) for a deep, narrow weld with a small heat-affected zone (HAZ) and minimum thermal distortion of the welded joint without significantly affecting the mechanical properties. In this study, S960QL base material (BM) specimens with a thickness of 15 mm were butt-welded without filler material at a welding speed of 10 mm/s using the high-vacuum (2 × 10−4 mbar) EBW process. Microstructural characteristics were analyzed using an optical microscope (OM), a scanning electron microscope (SEM), fractography, and an electron backscatter diffraction (EBSD) analysis. The macro hardness, tensile strength, and instrumented Charpy-V impact test were performed to evaluate the mechanical properties. Further, the results of these tests of the EBW joints were compared with the GMAW joints of the same steel grade and thickness. Higher hardness is observed in the fusion zone (FZ) and the HAZ compared to the BM but under the limit of qualifying the hardness value (450 HV10) of Q+T steels according to the ISO 15614-11 specifications. The tensile strength of the EBW-welded joint (1044 MPa) reached the level of the BM as the specimens fractured in the BM. The FZ microstructure consists of fine dendritic martensite and the HAZ predominantly consists of martensite. Instrumented impact testing was performed on Charpy-V specimens at −40 °C, which showed the brittle behavior of both the FZ and HAZ but to a significantly lower extent compared to GMAW. The measured average impact toughness of the BM is 162 J and the average impact toughness value of the HAZ and FZ are 45 ± 11 J and 44 ± 20 J, respectively.

Grain Refinement of Inconel 718 Superalloy—The Effect of Rotating Magnetic Field

The effect of the application of a rotating magnetic field on the average grain size of IN718 castings was experimentally studied. For the purpose, four parts were produced by investment casting and characterized. The first casting was produced without application of RMF for comparison. The remaining ones were submitted to different RMF frequencies for 15 min and subsequently to the pouring of the nickel-based superalloy. In these three castings, the RMF frequencies applied were, respectively, 15 Hz, 75 Hz and 150 Hz. All the other process parameters were kept constant during the execution of the experimental procedure. The average grain size of the samples was determined according to the ASTM E112-13 standard, using intercept methods. Macro hardness measurements, tensile testing and SEM-EDS analysis were conducted in order to evaluate the casting’s mechanical properties and microstructures. The results demonstrate a noticeable grain size reduction in the samples submitted to rotating magnetic field. An average grain area reduction, greater than 96%, was achieved in the castings where RMF frequencies of 75 Hz and 150 Hz were applied. The application of RMF also caused a morphological change in the casting’s dendrites from cellular to almost equiaxed. Additionally, it originated the decrease of the size and amount of needle-like δ phase. Regarding mechanical properties of the cast parts, no major differences were verified.

Effects of sintering techniques and parameters on microstructure and mechanical properties of Al-15Si-2,5Cu-0.5Mg compacts and Al-15Si-2,5Cu-0.5Mg/B4C composites

In this study, Al-Si compacts and Al-Si/B4C composites were produced from hypereutectic Al-Si alloy powders by cold pressing/conventional sintering and cold pressing/microwave sintering techniques. The effects of sintering temperature, sintering time and B4C particle addition on microstructural properties, density, hardness and transverse rupture strength were investigated. The phases and intermetallic compounds formed in the microstructure were determined by X-ray diffraction. Densities of the samples were measured by Archimedes’ technique. Macro hardness measurements were carried out with Brinell hardness test. Three-point bending tests were applied to the samples according to ASTM-B528–16. Elemental Al regions, master alloy (Al-Si-Cu-Mg) regions, primary Si particles and Cu- and Mg-rich secondary phases were determined in the microstructure. It was determined that the Cu- and Mg-rich secondary phases are θ(CuAl2), β(Mg2Si), γ(Al2CuMg) phases. An increase in porosity was determined in conventional sintered samples compared to green Al-Si specimens. In addition, it was observed that the amount of porosity increases, grain size and primary Si grains coarse with increasing sintering temperature in conventional sintering. The change in the amount of pores of the samples produced by microwave sintering without holding time at the sintering temperature is not as obvious as in conventional sintering. Similar microstructures were obtained in the samples at increasing sintering temperatures in microwave sintering. In the samples produced by conventional sintering, the hardness value decreased with increasing sintering temperature. Addition of 5 wt% B4C caused an increase in hardness at all sintering temperatures. The addition of 10 and 15 wt% B4C caused a decrease in hardness. In microwave sintering, the general trend in hardness change was a decrease with increasing B4C particle addition and increasing sintering time. Transverse rupture strength values close to and similar to each other in conventional sintered samples were obtained at different sintering temperatures. Transverse rupture strength values increased with the addition of 5 wt% B4C particles, and decreased with the addition of 10 and 15 wt% B4C particles.

Hot press sintering effects and wear resistance of the Al-B4C composite coatings of an AA-2024 alloy

Abstract In this study, the surface of AA-2024 alloy substrate was coated with an Al-B4C reinforced composite using hot press sintering. Al and B4C powders were synthesized by mechanical alloying. To this end, four samples were prepared. As a reference sample, AA-2024 substrate was coated with pure Al powder under 110 MPa pressure. In the other samples, the AA-2024 substrate was coated with metal matrix composites (MMCs) contained in Al-5 wt.-% B4C at 90, 110 and 130 MPa. The microstructure of the transition zone formed between the AA-2024 substrate and the coating layer of the coated samples, the microstructure of the Al/B4C MMCs coating, the macro hardness, the linear reciprocating and forth wear resistance of the coating layer were investigated. In addition, an optical microscope (OM), scanning electro microscope (SEM) images and EDS analysis of the microstructure were used. It was observed that the B4C powders were homogeneously distributed in the Al matrix in the microstructure of the coating layer. It was also found that the gaps between the grains in the microstructure of the coating layer and their size decreased with an increase in pressing pressure. Accordingly, it was concluded that macro hardness increased and weight loss decreased.

Mathematical Simulation and Experimental Verification of Carburizing Quenching Process Based on Multi-Field Coupling

Based on the multi-field coupling effect of temperature, diffusion, and phase change, the finite element model of carburizing and quenching was established. The 20CrMnTiH steel helical gear as the research object, prediction accuracy of carburizing, and quenching model of complex helical gear was studied. The material properties database of experimental steel was established by JMatPro, and the material thermophysical parameters needed in the calculation process were obtained. The carburizing and quenching process of transmission helical gear was numerically simulated by thermodynamic three-dimensional coupling analysis method combined with actual heat treatment process. The microstructure morphology, macro hardness, and deformation were characterized. The experimental results show that the microstructure of the hardened surface layer was acicular martensite and a small amount of residual austenite. The highest hardness appears at the surface layer of 778.8 HV, the effective hardened layer depth was 0.9 mm, and the maximum deformation of the gear was 0.055 mm. By comparing the experimental measurement results with the simulation results, they were in good agreement, which verifies the accuracy of the finite element model. This indicates that the model has good prediction ability in carburizing and quenching process.