Alloy Carbides Research Articles

Synthesis of Y2O3-doped WC-Co powders by wet chemical method and its effect on the properties of WC-Co cemented carbide alloy

Abstracts WC-8Co composite powders doped with Y2O3 were prepared by wet chemical method, and the densification of alloy proceeded by spark plasma sintering at 1200 °C, 1250 °C, and 1300 °C. The microstructure of the composite powders and alloys was analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. Result showed that the addition of Y2O3 could refine WC particles during carbonization and WC grains during sintering. In the microstructure of WC-Co alloys, Y2O3 solidly dissolved in the body of WC crystal with the form of the second-phase nanocrystal. Moreover, the effect of sintering temperature on WC-8Co cemented carbide doped with Y2O3 was studied. The comprehensive performance of WC-8Co cemented carbide doped with Y2O3 was best at the sintering temperature of 1250 °C with the hardness of 19.64 GPa and fracture toughness of 11.97 MPa m1/2.

Effect of prior cold ring rolling on carbide dissolution during the austenitizing process of an M50 bearing steel

The influence of prior cold ring rolling (PCRR) on carbide dissolution during the austenitizing process of an M50 bearing steel was investigated by combining microstructural observations with kinetics analysis. The microstructural results show that the PCRR leads to a reduction in the volume fraction and the mean diameter of the undissolved carbides. The matrix of the as-quenched specimens after PCRR is enriched with more carbon and alloying elements than those without PCRR, which further confirms that the dissolution behavior of the alloy carbides is enhanced by PCRR during the austenitizing process. The kinetics of the transformation from ferrite to austenite (α → γ) without and with PCRR are determined by differential scanning calorimetry (DSC) upon heating. The austenite onset (Ac1) and end (Ac3) temperatures both decrease with as the thickness reduction from the PCRR increases. The activation energy for the α → γ transformation is calculated and shows a significant decline when the PCRR process is applied. In addition, the PCRR process results in a slight increase in the hardness regardless of the austenitizing temperature.

Research on the intermediate phase of 40CrMnSiB steel shell under different heat treatments

In this study, 40CrMnSiB steel cylindrical shells were tempered at 350, 500 and 600 °C to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A mid-explosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40CrMnSiB steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 °C, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.

Effect of Long-Term Thermal Exposures on Tensile Behaviors of K416B Nickel-Based Superalloy

The effect of long-term thermal exposure on the tensile behavior of a high W content nickel-based superalloy K416B was investigated. The microstructure and the deformation characteristics were observed by scanning electron microscopy and transmission electron microscopy, and the phase transformation of the alloy during long-term thermal exposure was analyzed by X-ray diffraction patterns and differential thermal analysis. Results showed that after thermal exposure at 1000 °C, the MC carbides in the K416B alloy decomposed into M6C. During tensile deformation, dislocations slipping in γ matrix crossed over the M6C by Orowan bowing mechanism. With the increase of thermal exposure time, the secondary M6C reduced greatly the yield strength of the alloy at room temperature. Meanwhile, the continuous distribution of the secondary M6C with great brittleness in the grain boundary could become the main source of crack, which might change the fracture characteristic of the alloy from trans-granular to intergranular.

Effect of Tool Vibration on Flank Wear and Surface Roughness During High-Speed Machining of 1040 Steel

In recent years, the tool condition monitoring mechanism is necessary for analyzing the failure of the cutting tools in production practices. In a machining environment, steady and catastrophic failures of a tool are general faults associated with a machining process. The relationship between surface roughness, tool wear and vibration is explored during high-speed dry machining by using main input factor. L27 numbers of trials were performed in a CNC lathe with uncoated carbide CNMG120408 tool and alloy steel AISI 1040 workpiece. The predictable model is capable of expecting surface roughness (Ra), tool wear (VBc), and vibration of amplitude using observed data when turning alloy steel. The vibration was recorded only in the turning direction with a uniaxial accelerometer. Additionally, tool flank wear and finished work surface roughness are measured at various combinations of parameters. The outcomes of the work show that the axial feed rate is the main effective turning variable that influences surface roughness largely (91.97%). Optimization of turning process variables plays a significant role in turning to develop quality, manufacturing production rate and decrease production price. In this analysis, an advanced weighted principal component analysis strategy was initiated to optimize process variables in turning of 1040 alloy steel and the optimum relation was found to be d3 (0.5 mm)–f1 (0.06 mm/rev)–v3 (300 m/min). Higher depth of cutting along with largest cutting speed confirms the larger production rate which is desirable for industrial concern. Also, at the optimal setting, the excellent finish of surface with low wear and low acceleration is noticed with an improved S/N ratio of CQL from initial setting. However, the current work presented a better co-relation between tool vibrations, tool wear, and test surface finish which will be beneficial for the industrial uses.

Formation Mechanism of Microstructural Non-uniformity in the Hot Working of Commercial-Scale Electro-slag Remelted Alloy 690 Ingots

Microstructural non-uniformity in the wrought material of Alloy 690 is investigated in this study by analyzing the dissolution behavior of intergranular carbides, performing laboratorial forgings to explore the microstructural evolution rules and conduct industrial forgings to verify the laboratorial results. The intergranular carbides in Alloy 690 ESR ingots cannot be fully dissolved at a temperature < 1473 K (1200 °C), and undissolved carbides cause the appearance of carbide strips in the forged microstructure. Carbide strips are confirmed to be responsible for the formation of fine-grain bands in the wrought material by restricting the growth of nearby grains during annealing treatment. Industrial forgings agree well with the laboratorial tests, and it is recommended that in industrial practice the soaking temperature of large ESR ingots should be set between 1473 K and 1493 K (1200 °C and 1220 °C) for better carbide dissolution, and an evident ingot temperature drop prior to deformation should be avoided.

Comprehensive Processing of Basalt together with Magnetite Concentrate in Order to Obtain Ferrous Alloy and Calcium Carbide

Comprehensive Processing of Basalt together with Magnetite Concentrate in Order to Obtain Ferrous Alloy and Calcium Carbide

Effects of Various Factors on Interphase Precipitation of Nano-Sized Alloy Carbides in Low-Carbon Steels

Effects of Various Factors on Interphase Precipitation of Nano-Sized Alloy Carbides in Low-Carbon Steels

Evolution of microstructure and mechanical properties during tempering of M50 steel with Bainite/Martensite duplex structure

The evolution of microstructure and mechanical properties during tempering of M50 steel with bainite/martensite (B/M) duplex structure have been investigated. The microstructural observation shows that the redistribution of carbon atoms and precipitation of transition carbides in the B/M duplex specimens are slightly decreased during the initial stage of tempering, as compared with the fully martensitic specimens. After tempering of 550 °C, not only finer ferrite packets are obtained, but also the precipitation of nano-scale carbides is enhanced for the B/M duplex specimens. The mechanical characterization indicates that the hardness is decreased while the impact toughness is significantly improved when tempering temperature increases to 300 °C. When the tempering temperature increases to 550 °C, due to the decomposition of retained austenite (RA) and precipitation of alloy carbides, the hardness exhibits an obvious improvement while the toughness first decreases and then increases. The impact toughness of the B/M duplex specimens is higher than that of the fully martensitic specimens during the whole tempering process, although they have the same tendency varying with tempering temperature. Furthermore, the final wear resistance is significantly improved in the austempered specimens due to the enhanced precipitation during tempering.

3D Printing with Mixed Powders of Boron Carbide and Al Alloy

Laser additive manufacturing with mixed powders of boron carbide and aluminum alloy is investigated. Parameters such as laser power, scan speed, scan pattern, and hatching space are systematically evaluated and optimized to obtain the desired density and porosity. These results show that the AM part contains 20 wt% boron carbide and 80 wt% aluminum alloy, which are well mixed and synthesized during the melting process. Its mechanical properties are close to those of aluminum. A thin-wall structure based two dimensional and three dimensional radial collimators were fabricated with well-controlled geometry for neutron scattering measurement.

Effect of Silicon, Chromium and Molybdenum on Resistance to Temper Softening of Medium-carbon Martensitic Steel

The addition of alloy elements such as silicon, chromium and molybdenum is effective in the restraint of temper softening in martensitic steels. The martensitic steel containing such alloy elements is known to have excellent resistance to temper softening in low and high temperature tempering treatments. However, the effects of the compound addition and its mechanism have not yet been satisfactorily revealed. In this study, the effect silicon, chromium, and molybdenum on resistance to the temper softening of the medium-carbon martensitic steel was investigated. As a result, it is revealed that the temper softening resistance quantity is maximum at the tempering temperature 773 K in the martensitic steel containing silicon, chromium, and molybdenum; this is because of the miniaturization of cementite (θ) and clustering of (Cr,Mo,Mn) 2C. Moreover, it is revealed to form this cluster at a tempering temperature lower than the temperature at which the alloy carbide usually precipitates (823 K-873 K).

Mechanical & microstructural evaluation of reversible and irreversible embrittlement in ultra-high strength steel

This comprehensive study gives evidence of reversible and irreversible embrittlement in ultra-high-strength steel through destructive testing. Several tempering temperatures ranging from 350 °C to 700 °C were designated to observe temper embrittlement in the steel. Charpy impact, hardness, and tensile tests were performed for assessing the mechanical behavior of the steel. Stereo microscopy was utilized to examine the fractured surfaces and microstructural analysis was performed with the help of an optical microscope. During tempering, reversible temper embrittlement occurs due to the formation of alloy carbides between martensite plates while irreversible temper embrittlement is preferably due to the segregation of impurity elements (i.e. P and S) on grain boundaries as well as due to the coarsening of alloy carbides. It was found that irreversible temper embrittlement transpired when tempering was done in the range of 400–450 °C and reversible temper embrittlement occurred in 650–700 °C temperature range. Results of the notched-bar impact test clearly showed a reduction in impact toughness in susceptible temperature ranges; moreover, the revealed fracture surface and micrograph also validate these findings. Experimental results also validate that both types of embrittlement are detrimental to the mechanical properties owing to the decrease in hardness and tensile strength.

Influence of aging treatment on microstructure and properties of a novel spray formed powder metallurgy superalloy FGH100L

A novel nickel-based superalloy, designated as FGH100L, was prepared by spray forming, hot isostatic pressing and isothermal forging. Following this, the billets were subjected to different heat treatments including sub-solvus and super-solvus solution heat treatments. The microstructure stability and mechanical properties of the alloy during the long-term aging treatment at 760 °C were studied. During the aging treatment, the grain size did not change significantly in both of the sub-solvus and super-solvus alloys, but the recrystallization around the coarse grain boundaries occurred in the former. When the sub-solvus alloy was aged for 500h, some secondary γ′ precipitates coarsened and split at a critical size into doublet or octet of cubes and there were two sizes of tertiary γ′ precipitates. With the aging time extending from 1000h to 2000h, secondary γ′ precipitates continued to coarsen and split, but tertiary γ′ precipitates grew uniformly. When the super-solvus alloy was aged from 500h to 2000h, only tertiary γ′ precipitates with uniform size were seen and they tended to coarsen at approximately the same rate. After aging for 2000h, the carbides in sub-solvus and super-solvus alloys are mainly M23C6, which can improve grain boundary strength. For the sub-solvus alloy, with the extension of aging time, both the room temperature and high temperature tensile strength originally decreased, then increased, and finally decreased again. Meanwhile the room temperature plasticity decreased gradually, while the high temperature tensile plasticity increased first and then decreased. Compared with the super-solvus alloy, the sub-solvus alloy after long term aging exhibited superior high temperature tensile properties. Cutting γ′ precipitates by stacking faults and forming a continuous stacking fault by increasing the width of the stacking faults is another deformation mechanism of the sub-solvus alloy. In the super-solvus alloy there are still a large number of dislocations accumulating between γ′ precipitates, but only a small amount of superdislocations cutting γ′ precipitates.

Study of the effects of the laser remelting process on the microstructure and properties of the WC–10Co–4Cr coating sprayed by HVOF

The laser remelting technique is considered a promising and effective method for improving the surface of thermally sprayed coatings, eliminating microstructural defects such as pores and cracks, increasing the life of parts and equipment by increasing microhardness and increasing anchoring force between coating and substrate. In the present work, tungsten carbide alloy (WC–12Co–4Cr) coatings were deposited on properly prepared SAE 1016 substrates using the high velocity oxy-fuel technique. An ytterbium fiber laser was used to remelt the surface of the coating by accurately varying the scanning speed and laser beam power to achieve a pore and crack-free coating and better metallurgical anchorage to the substrate through the optimization of the studied parameters. The samples were characterized by scanning electron microscopy and microhardness. The results show that it is possible to obtain higher hardness coatings after the laser remelting process, free of pores or pronounced imperfections and metallurgically bonded to the substrate. We also found a processing range for the ytterbium laser remelting of the WC–12Co–4Cr coating aiming at high productivity and microstructural optimization of the coating for different thicknesses.

Effect of Silicon Carbide in Mechanical Properties of Aluminium Alloy Based Metal Matrix Composites

Metal Matrix Composites are a class of composites with evaluated properties that get another perspective of material structure and are generally utilized in the aviation and automobile industry. These materials have the properties of both the base matrix material as well as the reinforced materials. These metal matrix composites have low residual stress and thermal residual stresses. Due to this concept, the materials posses enhanced adhesive bonding between the matrix and reinforcements. Aluminium alloy with silicon carbide is applicable where hardness and toughness are the requirements. Metal Matrix Composites are designed in order to have the combined properties of both metals and ceramics. The specimens are fabricated for various proportions of the materials. In the fabrication, it begins with Aluminium alloy and Silicon carbide. The specimen is evaluated for diverse mechanical tests, and the experimental result is the pure aluminium undergoes more wear when compared to the reinforced specimen.

Design Analysis and Effect of Process Parameters on ‘Fsbw’ of Al (2618a)-SIC Alloy

The research in fabrication engineering is much focused on the new or betterment in the existing metal joining techniques. In the view of the demand in improvement of the quality , strength and efficiency of welded joins , the present research is focused on design for tensile strength and optimization of friction stir butt welding(FSBW)of aluminum(2618A) and silicon carbide alloy. The design analysis is carried out for tensile strength and hardness. . The functioning parameters such as tool rotational speed, transverse speed, plunge depth and tilting angle are considered. The Taguichi technique and ANOVA are used in optimization of process parameters. The high S/N ratios are mainly considered to analyze the results for tensile strength and hardness.

Performance Analysis of Chromium Carbide Overlay in Coal Nozzle Tip for Utility Boilers

Coal Nozzle Tip substrates are laid with chromium carbide alloy overlay to improve the performance life cycle of the component in power boiler. Overlay with hard faced materials exhibits better erosion / wear resistance of the components. Nozzle tips are located in front of the fire ball and gets heated up to 650 ºC due to radiations. The purpose of the investigation is to evaluate the performance of chromium carbide over lay in terms of life cycle. The Chromium rich tubular electrode was used to overlay on plate SA 240 type 309S substrate by Shielded Metal Arc Welding process. Test specimens were prepared for SEM/EDAX, microstructure analysis, hardness and jet erosion test. Surface hardness and jet erosion tests were carried out on hard faced surfaces at elevated temperature 600 ºC and 700 °C. Test results were analyzed and found that the Chromium carbide overlay resulted with low hardness and high erosion at elevated temperature with steeper impact angle.

Optimization of Texture Density Distribution of Carbide Alloy Micro-Textured Ball-End Milling Cutter Based on Stress Field

The insertion of micro-textures plays a role in reducing friction and increasing wear resistance of the cutters, which also has a certain impact on the stress field of the cutter during milling. Therefore, in order to study the mechanisms of friction reduction and wear resistance of micro-textured cutters in high speed cutting of titanium alloys, the dynamic characteristics of the instantaneous stress field during the machining of titanium alloys with micro-textured cutters were studied by changing the distribution density of the micro-textures on the cutter. First, the micro-texture insertion area of the ball-end milling cutter was theoretically analyzed. Then, variable density micro-textured ball-end milling cutters and non-texture cutters were used to cut titanium alloy, and the mathematical model of milling force and cutter-chip contact area was established. Then, the stress density functions of different micro-texture density cutters and non-texture cutters were established to simulate the stress fields of variable density micro-textured ball-end milling cutters and non-texture cutters. Finally, the genetic algorithm was used to optimize the variable density distribution of micro-textured cutters in which the instantaneous stress field of the cutters was taken as the optimization objective. The optimal solution for the variable density distribution of the micro-textured cutter in the cutter-chip tight contact area was obtained as follows: the texture distribution densities in the first, second, and third areas are second, and third areas are 0.0905, 0.0712, and 0.0493, respectively.

Weak influence of ferrite growth rate and strong influence of driving force on dispersion of VC interphase precipitation in low carbon steels

Dispersion of nano-sized alloy carbides formed by interphase precipitation at migrating ferrite/austenite interphase boundaries is expected to be affected by local conditions at the boundaries, including ferrite growth rate and driving force for precipitation. The effects of these two factors were systematically investigated by changing alloy composition and transformation temperature. Quantitative analyses by using three-dimensional atom probe reveal that VC interphase precipitation becomes higher in number density and smaller in size at lower transformation temperature or with higher V content. The dispersion of VC is also slightly refined by lower Mn or higher Si content, but remains almost unchanged by increasing the C content. Such variations show good correlations with the driving force for its precipitation that finer VC precipitates can be obtained by enlarging the driving force. In contrast, the influence of the ferrite growth rate on the dispersion in most cases is quite small in the range of this study, which can be explained by considering nucleation kinetics of VC at migrating ferrite/austenite interface.

Effects of Q&T parameters on phase transformation, microstructure, precipitation and mechanical properties in a PS-30Cr2Nb pipeline steel

The heat treatments with different quenching and tempering temperatures were conducted to clarify the effects of Q&T (quenching and tempering) parameters on phase transformation, microstructure, precipitation, mechanical properties in a PS-30Cr2Nb pipeline steel. Results indicate that the optimum property of tensile strength of 892 MPa and elongation of 19.17% was obtained at a low quenching (950 °C) and low tempering temperature (570 °C). Finer prior austenite grains and carbides contributed to the higher strength. Besides, the content of coarsening carbides increased with tempering temperature and quenching temperature. The increased content of coarsening carbides is responsible for the deteriorative comprehensive performance. In addition, Fe3C particle was gradually substituted by the alloy carbides with the proceeding of tempering by the dynamic assignment of elements.