Papers by Keyword: Carbide

Abstract: This study aimed to smelt high-entropy alloys (HEAs) composed of inexpensive and commonly available metallic elements using iron-based alloys, ligatures, and commercially pure metals, and to investigate their phase structure and heat-resistance. High-entropy alloys of the FeNiCrCuAl system were smelted in air using an induction furnace with a crucible lined with rammed neutral aluminum and magnesium oxides. The elements Fe, Ni, Cr, Cu, and Al were introduced via high-alloy cast iron, stainless steel grade GX10CrNiMn-18-9-1 (1.4541), industrial-grade low-carbon ferrochrome (FeCr70C1), binary Cu-33Al ligature, tough-pitch copper, and semi-finished nickel. Samples of the investigated alloys were prepared using lost foam and sand mold casting methods. Microstructural analysis revealed the presence of rounded dendritic branches, copper-rich interdendritic regions, and high-chromium carbides. The phase composition of the as-cast FeNiCrCuAl alloys consisted of multiple phases: solid solutions with a BCC structure ordered in the B2 type, an FCC structure, and complex carbides (FeCr)₇C₃. High-entropy alloys of the FeNiCrCuAl system, with increased aluminum and chromium content, can significantly outperform standard heat-resistant stainless steels in terms of oxidation resistance indicators – surface oxidation rate, and oxidation stability at 900°C and 1000°C. The specific oxidation of the high-entropy alloy FeNiCrCuAl, which contains at least 18 at. % chromium, was 0.1627 mg/cm² after a 4-hour exposure at 1000 °C. Under the same conditions, the specific oxidation of X2CrNi19-11 stainless steel (1.4306) was 0.6689 mg/cm².

Abstract: The study aims to determine the load contributes to changes in the tensile strength of steel P22 at high temperatures. The steel sample was loaded under 95 and 125 N at a temperature of 700 °C for 72 hours. The results showed that the strength of P22 decreased with increasing load. At the temperature of 700 °C, the yield strength (YS) value decreased from 200 to 182 MPa and the ultimate tensile strength (UTS) reduced from 353 to 321 MPa as the load increased from 95 to 125 N. The precipitation of carbide in the matrix of P22 was observed in the steel sample loaded under 125 N at 700 °C for 72 hours. Furthermore, the cavity formation located on the boundary and near the carbide was confirmed when the temperature was 700 °C and the load increased from 95 to 125 N. The cavity was proof of a stress increase near the grain boundary, causing a decrease in the steel’s strength after a certain period of working time at high temperatures.

Abstract: Carbide machining process brings a whole range of problems in practice. This mainly concerns problems associated with their machinability and the economy of the applied machining technology. Because of these problems, it is often not possible to use traditional production technologies when machining them. However, progressive machining technologies achieve relatively good results. However, even with progressive technologies, the problem with the overall efficiency of the machining process remains. Therefore, experimental research was carried out, the aim of which was to obtain relevant data regarding the quantification of qualitative indicators of the machined surface during the machining of hard metals through progressive electrical discharge technology in relation to the overall economic efficiency of the machining process. As part of the conducted experimental research, partial data of individual elements were obtained on the basis of which complex conclusions were drawn in mutual contexts. Subsequently, complex data regarding the effectiveness of the applied electrical discharge process in the machining of hard metals were summarized.

Abstract: Adaptation of the previously developed methodology for assessing risks and opportunities for assessing risk situations and identifying opportunities during operation of built-up cutting tools is made. The factors influencing performance of built-up cutting tools are analyzed. The article presents an analysis of failures of replaceable inserts of built-up cutting tools when performing face milling operations, the results of which will be taken into account when applying the developed technique.

Abstract: In cutting process, the wear of the tool remains posed, it describes their progressive failure in regular operation. The tool wear phenomena is mainly caused by abrasion of hard particles, shearing of micro welds between tool and work-material and the exchange of particles between the tool and work material leading to a several forms of tool wear, however, we focused in this study on the frontal wear, also called wear on clearance surface or flank wear. For efficient use of cutting tool according to the technical requirement, the comprehension and the knowledge of the cutting tool wear evolution is necessary. In order to meet this indispensable need, the present paper proposes a two-step tool flank wear monitoring technique based on vibratory signals analysis during the turning operation using a P30 grade metal carbide tool and C45 (XC48) steel. Firstly, discrete wavelet transforms (DWT), has been used to decompose the signal and extract the information, then the scalar indicator Root Mean Square (RMS) value has been used to evaluate the cutting tool stability level. The proposed method offers the possibility to accurately predict break-in tool wear phase, accelerated tool wear phase and the stability period, in which a high quality machining process is guaranteed.

Abstract: Recently, stress, strain, strain-rate dependent curves for cemented carbide have become an established tool for evaluating the mechanical properties. In this paper, related strain-rate dependent data of a K05 insert were employed to define the developed stress and strain fields occurring in the compound coating-substrate at impact forces of various durations. In this way, the occurring maximum strains at various impact loads and times were analytically calculated. These maximum values and related fatigue endurance coating strain-rate dependent limits were consequently used to validate published coating fatigue critical impact forces associated with certain impact times.

Abstract: This paper describes simple metallographic technique for selective etching of individual types of carbides (MC, M₂C and M₆C and M₇C₃) in tool steel. Electrolytic etching in chromic acid was used in order to reveal the MC carbides. Chemical etching in permanganate solution revealed the M₂C and M₆C carbides, while the electrolytic etching in the latter solution enabled to observe M₇C₃, M₂C and M₆C carbides. These techniques were demonstrated on an experimental niobium-containing tool steel prepared by powder metallurgy. The results confirm that the MC carbides are highly thermally stable, while the M₂C carbides decompose during austenitizing at the temperature of 1050 °C and higher. The M₇C₃ carbides dissolve in the austenite significantly. This exact and simple observation of the carbides behaviour enables to describe the role of particular carbides on heat treatment behaviour and also to save the carbide-forming elements, where the important ones (tungsten, vanadium) are listed as critical raw materials and the others (chromium and molybdenum) are also strategic.

Abstract: Machining process usually involves relevant wear effects on the cutting tool, producing undesirable surface features on the work-pieces. Lubricants and cooling fluids are used with the aim to minimize the wear phenomena as well as high temperatures produced during the cutting processes. However, the use of these fluids may have an adverse environmental impact. For this reason, the reduction of quantity of cutting fluids used in the machining process is a requirement in order to improve the performance and sustainability of the process. For this purpose, this work proposes an increase of the lubricant retention ability for cutting tools based on surface modification. In this research, micro-geometrical features of Carbide (WC-Co) surfaces have been modified by laser texturing techniques. A wide range of roughness topographies had been developed by changing the laser irradiation parameters of energy density of pulse (E_d) and scanning speed of the beam (V_s). Different geometries of the textured tracks (single spots, linear tracks, circular tracks) also were studied. Moreover, through specific roughness features conducted by texturing process, the retention ability of cutting fluids was modified. It was evaluated by the contact angle between liquid and solid phases. This modification allowed to increase the self-lubricant effect of the WC-Co surface. This methodology has been validated on carbide tools under lubricated machining processes. Wear effects on the cutting tool were reduced and the surface finish of the machined parts was remained at least in the same ranges as non-modified tools.

Abstract: Iron-based alloys (steel and cast iron) are currently the main structural materials that provide a high level of mechanical and technological properties along with a relatively low cost. Increasing the performance characteristics (tensile strength, hardness, wear resistance, corrosion resistance and, ultimately, service life) of cast irons and steels is an urgent task. The quality of castings made of cast iron and steel depends on many technological parameters that affect the processes of crystallization of the melt (casting temperature, molding mixture, chemical composition, volume of casting, overheating of the metal during smelting, etc.). It is possible to improve the quality of castings without changing the technology of smelting and pouring metal into molds, if you learn how to manage the crystallization process. The laboratories have grown defect – free iron crystals with a tensile strength of more than 1000 kg/m2 (strength of carbon steel-40 kg/m2). Attempts to improve the mechanical properties by creating a single crystal are not justified, so you have to go the opposite way-to influence the crystallization process to get a lot of small crystals (grains), which also allows you to achieve high mechanical properties. The dependence of the strength characteristics on the grain size is well described by the law of Hall-Petch, according to which when the average grain size is reduced by 3...5 times there is an increase in the hardness of the material, with a further decrease in the average grain size by more than 10 times – an increase in plasticity. Influence on the processes of crystallization of iron and steel melts (change the size of metal grains, change the shape, size and distribution of graphite inclusions) can be the introduction of small additives substances (modifiers), not chemically interacting with the matrix. The use of modifiers to increase the rate of crystallization, reduce the structural heterogeneity of castings has good prospects. In addition, unlike doping, modification does not require a large number of expensive additives and, accordingly, slightly increases the final cost of production.

Abstract: Sintered steels, with and without boron addition, were prepared from powder compacts of pre-alloyed Fe-1.5Mo powder mixed with varied amounts of graphite (0, 0.1, 0.2, 0.3, and 0.4 wt.%) and hexagonal boron nitride (0 and 0.5 wt.%). Sintering was performed either in hydrogen or in vacuum atmosphere at 1280 °C for 45 minutes. The post-sintering cooling was performed in a furnace that was equivalent to 0.1 °C/s. The sintered boron-free steels showed dual-phase microstructure consisting polygonal ferrite and precipitate-containing grains. Each precipitate-containing grain contained packets, each of which was characterized by lamellar structure with alternating fibrous particles and ferritic laths, when carbon contents were in the range 0.1-0.3 wt.%. All the grains containing fine needle particles decorating ferritic lath boundaries were observed in the sintered Fe-Mo-0.4C steels. Boron addition caused some effects on sintered steels. The action of boron was the formation of grain boundary boride in the vacuum-sintered steels although it was hardly observed in case of hydrogen-sintered steels. Boron also promoted precipitation inside polygonal ferrite grains and along ferritic lath boundaries. The precipitate particle shape was fine needle-like in the sintered boron-containing steels. Due to liquid phase sintering, as a result of eutectic melting, the associated grain growth was observed. Disappearance of grain boundary boride was evidenced in the hydrogen-sintered steels. Without boron addition, hardening of the sintered steels strongly depended on carbon content. With boron addition, all the sintered steels showed high tensile strength and hardness even in the case of no graphite addition. Hardening action by carbon in the sintered boron-containing steels was weaker than that in the sintered boron-free steels.