This article describes a procedure using flame atomic absorption spectrometry for specimen preparation to quantify tungsten in alloyed tool steel and high-speed steel. The sample solution was ...prepared using a microwave-assisted digestion with a mixed acid of hydrofluoric, nitric, and phosphoric acids. Vanadium was added as an internal standard element to the sample solution to measure tungsten and vanadium absorption lines simultaneously using a spectrometer equipped with a multi-wavelength system, which comprised a xenon lamp as a continuum light source and an echelle grating. The internal standard method, with its tungsten-to-vanadium absorbance ratio, contributed to accurate and precise quantification of high-content tungsten in tool steel samples.
This paper describes an improved microwave digestion procedure for steel samples of various kinds intended for inductively coupled plasma atomic emission spectrometry, including low alloy steel, ...stainless steel, alloyed tool steel, and high-speed steel. Their resulting solutions were used for the simultaneous quantification of alloyed elements together with several light elements of boron, aluminum, silicon, and phosphorous. Conventional digestion methods, using materials such as hydrochloric and nitric acids including aqua regia, and sulfuric and phosphoric acids with a fuming treatment, showed poor ability to decompose certain steels completely or to be simultaneously quantified with some elements. By contrast, microwave digestion with an acid mixture of hydrochloric acid, hydrofluoric acid, nitric acid, sulfuric acid, and distilled water with a 2:1:1:1:5 volume ratio fully decomposed various steel samples. For inductively coupled plasma atomic emission spectrometry, the suggested procedure is applicable to quantify boron, aluminum, silicon, phosphorous, titanium, vanadium, manganese, cobalt, copper, molybdenum, and tungsten.
Novel Fe68(MoWCrVCoNiAlCu)32 (at.%) medium-entropy high-speed steel (ME-HSS) coatings, containing various carbon contents from 0.65 to 1.05 wt%, are prepared by laser rapid solidification. The newly ...prepared ME-HSS coatings are characterized by a hard martensitic matrix enhanced by secondary hardening, and specifically by coherent nano-sized M2C. The secondary hardening effect is enhanced with the increasing carbon content. The high amount of alloying elements in ME-HSS coatings results in excellent oxidative wear resistance, without leading to serious compositional segregation and coarsening of carbides.
Microstructure and hardness variation of novel Fe68(MoWCrVCoNiAlCu)32 medium-entropy high-speed steel (ME-HSS) coatings with different C content: 0.65 wt%C (ME-HSS-065C), 0.85 wt%C(ME-HSS-085C) and 1.05 wt%C(ME-HSS-105C). Display omitted
•New medium-entropy high speed steel coatings exhibit excellent hot wear resistance•Secondary hardening due to coherent nano-sized M2C contributes to the high hardness•The secondary hardening is enhanced with the increasing C content•The C content needs to be optimized for high hardness and good hot wear resistance
At 600 °C, a TiB2-Al2O3-Ti(20 %) coating was deposited by electron beam deposition (EBD) on high-speed steel (HSS) substrates. X-ray diffraction and field emission scanning electron microscope and ...energy-dispersive X-ray spectroscopy were used to investigate the structural analysis and surface morphology of TiB2-Al2O3-Ti(20 %) coating. The effect of load on Young’s modulus and hardness was studied using mechanical experiments on TiB2-Al2O3-Ti(20 %) coatings at modest loads ranging from 2000 to 10000 µN. Nanoscratch was done on TiB2-Al2O3-Ti(20 %) coated on HSS and uncoated HSS sample at a low load of 0–10000µN, and the coated sample had a COF of 0.08–0.21, whereas the uncoated sample had a COF of 0.2–0.46. To investigate the deformation and failure behavior of the coating/substrate combination and their nanotribological properties, nano wear experiments were done on TiB2-Al2O3-Ti(20 %) coatings at loads ranging from 0.5 N to 2 N. The results demonstrate that Young’s modulus and hardness of the TiB2-Al2O3-Ti(20 %) coating decreases when the load increases. The TiB2-Al2O3-Ti(20 %) coating has a coefficient of friction(COF) ranging from 0.08 to 0.17, indicating that it is self-lubricating, whereas the COF of uncoated HSS is 0.1–0.58. With increasing stress, the wear rate of TiB2-Al2O3-Ti(20 %) coating grows from 2.6808 × 10−3 to 4.461 × 10−3 mm3/m, while uncoated HSS wears from 6.4367 × 10−3 to 21.2 × 10−3. The TiB2-Al2O3-Ti(20 %) coating had smooth wear scars having no cracks/debris on the sample surface, indicating that the coated material flowed near the wear scar in a plastic manner.
With the rising need to promote productivity that is based on quality, energy, and cost, it is imperative that cutting tools are not just selected on the basis of its suitability, but on its ...efficiency. It is particularly important that workpiece materials are aligned to specific cutting tools, to improve manufacturing costs, lead time, and quality of the overall product and to create flexibility. For this reason, a comparative study of the performance of high-speed steel and tungsten carbide cutting tools has been performed to determine the most suitable for the machining of a 304 Austenite Steel cylindrical bar. The tool wear of the cutting tools was selected as a measured to ascertain their performance in the turning operation. Response surface methodology was employed to analyzing the results and determining their optimal performance. From the study, the tungsten carbide tool recorded optimal parameters as follows: cutting speed 1303 m/min, feed rate 0.354 mm/rev, and depth of cut 0.458 mm with a tool wear of 1.173 mm and for the high-speed steel tool, cutting speed 1321 m/min, feed rate 0.208 mm/rev, and depth of cut 0.682 mm with a tool wear of 2.073 mm. The study judging from the tool wear shows the efficiency of the tungsten carbide tool over the high-speed steel cutting tool, as it can be seen from the results obtained that the lowest tool wear in the turning of the cylindrical steel bar is recorded from the use of the tungsten carbide cutting tool. From the 3D surface plots, it can be confirmed that to obtain a good performance from the different cutting tools, the cutting speed best suited for the cutting tool must be taken into consideration.
In the current study, crack-free M2 high-speed steel (HSS) was produced by selective electron beam melting (SEBM) under different volumetric energy densities (VED, 40–56.3 J mm−3) and high powder bed ...preheating temperatures (PBPT, 750 °C and 820 °C). Results show that fully dense M2 HSS can be achieved under the VED of 43.6–47.9 J mm−3 and PBPT of 820 °C. Moreover, SEBM M2 HSS mainly consists of less than 7 µm α-Fe matrix grain as well as fine carbide, which were induced by high cooling rate of the molten pool. The fully dense sample presents ultra-high hardness (∼70 HRC) and excellent tribological properties. Its wear rate is 13.7 % lower than that of quenched and tempered wrought bulk counterpart.
Depending on various properties such as hardness, roughness, friction coefficient, wear resistance, and oxidation behavior, different grades of steel can be used in hot strip mills. In this paper, ...two grades were investigated: one grade of semi-high-speed steel and one grade of high-speed steel. They differ in their chemical composition, principally the carbon and the chromium content, and the presence or not of other alloying elements such as vanadium, niobium, and tungsten. Their oxidation behavior was studied at 576 °C and 600 °C, temperatures reached in the F1 finishing stand and the roughing stand, respectively, by high-temperature oxidation tests in a wet atmosphere. The sliding wear resistance was followed by pin-on-disc experiments. The evolution of the microstructure was observed by optical and scanning electron microscopies. The oxides formed on the surface of the samples were analyzed by XRD and EDS. The thickness of the oxide layers and the mass gain were measured from oxidation tests. The results showed that for both grades, the surface roughness
R
a
after oxidation tests is high enough to prevent slipping. The low friction coefficient will increase the wear resistance of the roll. The hardness of the steel grades decreases but remains high enough to ensure wear resistance. Consequently, those grades can be used in the roughing stand or the F1 finishing stand of hot rolling mills.
•This study provides the first systematic evaluation on nanoindentation deformation behaviour on an oxidized HSS surface by both experiment and modelling.•A finite element model considering practical ...microstructural features (thickness and porosity) of oxide scale has been developed and verified by experimental results.•Obvious nanoindentation size effect was observed and three regions can be distinguished based on the maximum nanoindentation depth.•Friction has only a slight influence during nanoindentation, but porosity in oxide scale has a great effect.
In the present paper, a systematic study on the deformation behaviour of an oxidized high speed steel (HSS) during nanoindentation has been conducted. Specimens cut from a HSS work roll were oxidized first to develop the oxide layer with thickness close to that built up on a HSS work roll surface during hot rolling in industry. Then, nanoindentation tests with three typical peak loads from low to high (namely 2 mN, 20 mN, and 200 mN) were conducted on the oxide scale surface. Porosity in oxide scale and its surface morphology features were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. In addition, a finite element model was developed and verified by comparing with the experimental measured load-depth curves. With the developed model, for the first time, a systematic investigation has been done to understand the effects of nanoindentation depth (from 10 nm to 1250 nm), friction coefficient (from 0 to 0.6) and initial porosity of oxide scale (from 0 to 20%) during nanoindentation on the deformation behaviours of both oxide scale and HSS substrate. It has been found an obvious size effect and three regions can be divided according to nanoindentation depth, based on the evolution of mechanical property, porosity in oxide scale, and plastic deformations in both oxide scale and HSS substrate. This study also revealed that friction has a slight influence during nanoindentation and almost the same results were obtained when the friction coefficient is larger than 0.3. By contrast, a large influence of porosity in oxide scale was observed.
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The effects of RE and Ti microalloying during electroslag remelting (ESR) process on the microsegregation and morphology of eutectic M2C carbides in M2 high speed steel were investigated. The results ...show that the addition of 0.2 wt% RE can alleviate the segregation of C, W, Mo, V and Cr, while the morphology of eutectic M2C carbides hardly changes. The microalloying with the addition of 0.5 wt% Ti has the lowest degree of microsegregation due to the improvement of primary dendrites by the effective heterogeneous nucleating agent of (Ti,V) (C,N) particles. The addition of Ti makes the morphology of M2C carbides change from rod-like or maze-like shape into a coarse feathery shape, exhibiting anisotropic facet growth characteristics. For the microalloying of 0.2 wt% RE and 0.5 wt% Ti, the segregation of the main metal alloying elements is slightly more severe than that of the addition of only RE or Ti. Under the combined action of RE and Ti, the feathery eutectic M2C becomes thinner and shorter and tends to be isolated or distributed in a discontinuous network.
In-situ Ti microalloying during ESR significantly reduces dendritic segregation of M2 high speed steel, and changes the morphology of M2C carbides from rod-like or maze-like to coarse feathery shape. In-situ Ti and RE composite microalloying improves the feather-like M2C carbides, making them thinner and shorter, and tends to be isolated or distributed in a discontinuous network. Display omitted
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