クロム/高速度工具鋼混合粒子を用いた真空置換 AIH-FPP 処理による炭素鋼の表面改質

In recent years, weld cladding has become an emerging technique for the surface modification of carbon steel, which has various industrial applications such as chemical, marine, mining, agriculture, and power generation. In this research, cold metal transfer (CMT) welding and pulse metal inert gas (MIG) welding are utilized to study the weld-clad bead of 308L stainless steel over low-carbon steel. To examine the mechanical and wear characteristics of CMT weld-clad samples, welding speed (3, 4, 5, and 6 mm/s) was used as the input process parameter, while current (175 A), nozzle to workpiece distance (10 mm), and shielding gas flow rate (15 l/min) were kept constant. Microstructural analysis of weld bead samples was done through optical microscopy and field emission scanning electron microscopy. With an increase in welding speed, the microhardness and wear properties of the clad surface were improved. The CMT-clad surface had significant improvements in mechanical, wear properties, and lower residual stresses due to low dilution and lesser heat input.

In the field of mechanical engineering, engineers are always looking for ways to improve the properties of materials. Cryogenic treatment of tooling steels is a proven technology to increase wear resistance and extend intervals between component replacements. The main idea of this paper is to apply Taguchi method to optimize cutting parameters in turning operation using cryogenic treated (CT) and untreated (UT) high speed steel (HSS) tools, so that the scope of cryogenic treatment on HSS tool material may be presented for the benefit of medium and small scale industry using HSS tools for cutting operation. Taguchi L25 orthogonal array is employed to study the performance characteristics in turning operations of AISI 1020 steel bars using CT and UT HSS tools. The microstructure has been found more refined and uniformly distributed after cryogenic treatment of HSS tool. It has been observed that optimum machining parameters in both the cases (CT HSS and UT HSS tools) are higher cutting speed (49.9 to 75.7 m/min.), lower feed rate (0.15 mm/rev.), medium depth of cut (0.40 mm). Analysis of variance (ANOVA) indicates that the cutting speed is most significant parameter followed by feed rate in case of CT HSS tool and depth of cut in case of UT HSS tool.

The fact that samples prepared by a high frequency induction melting and centrifugal casting method is excellent in uniformity suggests that this method is adequate for the preparation of tool and high speed steel samples containing a large amount of carbide-forming elements for instrumental analysis. In this study remelted samples which were prepared from tool (JSS 600∼605) and high speed (JSS 606∼611) steels for chemical analysis by this method were analyzed in comparison with the same standared samples for instrumental analysis. The method for the assessment of the remelted samples was as follows. The equations of the working curves were derived from the data for the standard samples for instrumental analysis by curve fitting with orthogonal polynominals. The F-test was performed for comparison of the mean squares of both data. Emission spectral analysis (Cu, Ni, Cr, Mo, V, W) and X-ray fluorescence analysis (Ni, Cr, Mo, V, W) of tool steels showed that some of the standard samples gave abnormally higher values in tungusten analysis. The working curves successfully constructed from the standard samples when excluded those samples with abnormal tungsten content and included Fe-W alloy samples (JSS FXS 375∼378). In order to make clear the cause of this higher analytical value, the microstructures were investigated with an optical microscope and an electron probe X-ray microanalyzer. It was inferred as a main cause that comparatively large tungusten carbide scattered non-uniformly in one standard sample, while there was no carbide in the remelted samples. In X-ray fluorescence analysis (Co, Cr, V, Mo, W) of high speed steels, there was a discrepancy in analytical values of vanadium between the standard sample and the remelted one with a high vanadium content (V: 3.19%), and the analytical values of tungsten in the high tungsten standard samples showed considerable scattering in positive errors. Microstructure observations confirmed that the positive errors were due to the presence of coarse unmelted carbide in the standard samples.

The finite element analysis for the tubular alumina liner which was shrink-fitted into a heat treated high speed steel (HSS) sleeve and subjected to high inner pressure and high temperature was performed. The parameters for the analysis were the interference between the alumina and the HSS, the temperature, the inner pressure, the coefficient of friction between the alumina and the HSS, and the taper at the sleeve ends. From the analysis, it was found that the tensile hoop stresses were decreased when the end parts of the HSS sleeve were tapered and the tensile stresses were decreased as the coefficient of friction between the alumina and the HSS was decreased. Also it was found that the alumina might be used as the structural liner for high pressure and high temperature when it was shrink-fitted into a heat treated HSS sleeve.

Harmonic structured materials with fine and coarse grains demonstrate not only enhanced strength but also enough ductility simultaneously. The harmonic structured material consists of a network like a fine grain region and a dispersed coarse grain region. The high strength and enough ductility are attributed to the network fine grain region and the dispersed coarse grain region, respectively. In this study, the harmonic structured metallic composite with high speed steel (HSS) and low carbon steel (LCS) is fabricated by mechanical milling and spark plasma sintering process. The harmonic structured HSS/LCS composite consists of the network like fine grain region with HSS and dispersed coarse grain region with LCS. The hardness of the harmonic structured composite with HSS and LCS is higher than the conventional particle dispersed composite with the same HSS volume fraction.Furthermore, the harmonic structured composite with HSS and LCS indicates high tensile strength without ductility loss, compared to the conventional HSS particle dispersed composite with the same HSS volume fraction. The harmonic structure control of composite materials is effective to improve the mechanical properties with enough ductility maintained.

Manufacturing industries are presently using many tool materials, such as high speed steel, carbide tool and diamond tools etc. The most widely and commonly used tool in the engineering industries is high speed steel (HSS). The HSS tools are the cheapest and reliable for medium and small scale industries. In this work, the HSS single point cutting tool is taken as substrate material and coated with two different combinations of TiAlN composite coating using Physical vapour deposition (PVD) technique. Also, Tool life was calculated and compared with uncoated HSS tool. The hardness and surface roughness value for both the tools have been taken under same condition. The loss of weight in the tool after machining has been weighed using standard equipments. The differences have been closely observed with sufficient trials and find out the loss in weight in both the tools. The weight loss percentage was calculated after proper machining trials. The tool life of the Titanium Aluminium Nitride (Ti 70%, Al 25%) coated tool has been increased by 3.74 times than that of uncoated tool. The surface finish for TiAlN (Ti 70%, Al 25%) coating is better than the uncoated tool. The PVD coated tools having better performance comparing with uncoated HSS tool.

A method for determining the tin content of plain carbon, stainless and high-speed steels by use of an atomic-absorption technique with electrothermal atomisation is described.Careful selection of the conditions under which the steel samples are dissolved makes it possible to obtain final solutions with approximately the same concentrations with respect to nitric acid. In consequence, it is possible to analyse all of the steels examined by using the same calibration graph. The proposed method is free of interferences from the other components normally present in steels and is suitable for analysing samples with a tin content in the range 0.002–0.040%.The proposed method provides rapid and accurate results and is suitable for routine analysis.

This paper describes the adhesions of 18-8 stainless steel to various tool materials (carbon Steel, High Speed Steels, Carbides and Ceramic) on the basis of the friction tests. Adhesions of 18-8 stainless steel to tool materials can be avoided by preventing the bare Austenitic structure from the contact of the tool materials as much as possible. One way for attaining this purpose is an application of cutting fluid containing extreme pressure agents and the other is to vary the structure of 18-8 stainless steel-for example, from Austenite to Martensite. The results are as follows : (1) At higher speed, Carbide with sulphurized oil (active) is best and at lower speed, High Speed Steel with sulphurized oil (active). (2) Low temperature cutting with Carbide is effective for preventing adhesions of 18-8 stainless steel.

The active screen plasma nitriding technique has been studied in recent years as a method to optimize surface properties in steel components, avoiding the negative effects caused in the conventional Direct Current plasma treatments. In this study, ASTM M2 high-speed tool steel samples were plasma nitrided with and without the use of the active screen, in order to compare the surface properties developed by each technique. The treatments were carried out at 500 °C, with the gas mixture of 76 vol.% N2 + 24 vol.% H2 , for 4 and 8 h. The active screen used was built with an expanded sheet of 304 stainless steel. The results were evaluated through optical microscopy, X-ray diffraction, and microhardness measurements. The samples were subjected to dry ball-on-flat tribological tests and the wear tracks were verified by 3D optical interferometry. The active screen use provided the formation of thinner layers, however, avoided the formation of brittle phases, resulting in the lowest wear volumes observed, up to 10 times less than the other analyzed conditions (nitrided and non-nitrided samples).

Microstructure and properties of laser surface hardened M2 high speed steel

Effect of Mischmetal on As-cast Microstructure and Mechanical Properties of M2 High Speed Steel

In the present paper, the microstructure and properties of laser surface hardened M2 high speed steel have been studied. The influences of preheat treatment processes, post heat treatment processes and laser parameters on the properties of the laser treated zone are also investigated. It was shown that the surface hardness and softening resistance of M2 high speed steel are evidently increased with laser surface hardening. The M2 high speed steel which is quenched at 1220°C and triple tempered at 560°C for 3 h has higher hardness after laser surface hardening. The grain size of laser hardened zone is much smaller than that of the traditional quenched high speed steels at different quenching temperatures. The amounts of retained austenite and undissolved carbides are decreased, and disperse carbides precipitate during laser surface hardening.

The tribological tests of a ferritic stainless steel (FSS) 445 in contact with high-speed steel (HSS) were performed on a high-temperature pin-on-disc tribometer. Wear exhibited significant difference when the FSS 445 was oxidised with a Cr-rich oxide scale on the surface. The HSS pin displayed adhesive wear when there was no oxide scale on the stainless steel disc, and in the early stages, the coefficient of friction fluctuated significantly, but the level of wear changed as Cr2O3 particles formed. The wear was then reduced, and the coefficient of friction remained stable. The Cr-rich oxide scale which formed on the stainless steel was able to stabilise the coefficient of friction, to reduce the wear rate and to help form a glazed layer on the HSS surface. The abrasive wear of the HSS pin took place at 850 °C, indicating that the hardness of the Cr-rich oxide scale increased as the temperature decreased.

The article aims to comprehend the microstructural changes, in Plasma Transfer Arc (PTA) deposited M2 high speed steel (HSS) hardfacings upon incorporation of 10 wt% Mo alloying during deposition followed by laser surface melting. PTA deposited hardfacings were produced over 4140 steel. Then Mo alloyed and unalloyed PTA deposits were subjected to laser surface melting (LSM) process. A comprehensive microstructural characterization for all the resultant structures was carried out. Optical metallography using appropriate etching reagents and SEM microscopy in conjunction with XRD techniques were employed to ascertain the matrix structure and carbides morphology. The PTA microstructure was close to equilibrium structure of M2 HSS containing mixture of ferrite/austenite/martensite along with MC, M2C and M6C type carbides. While the LSM of M2 HSS caused higher fraction of martensite and finer grains in the structure resulting in increment in hardness. 10-wt% Mo addition changes the carbides from MC and rod like M2C to fibrous M2C and fishbone like M6C carbides. The LSM of Mo alloyed M2 HSS PTA deposits led to an overall decrease in the fraction of M6C carbides and fibrous M2C carbides accompanied by a decrease in hardness.

High speed steels are ferrous based alloys of the Fe–C–X multicomponent system where X represents a group of alloying elements comprising mainly Cr, W or Mo, V, and Co. These steels are mainly used for cutting tools, since they are characterised by their capacity to retain a high level of hardness while cutting metals at high speed. The as cast microstructure of high speed steels consists of dendrites surrounded by a more or less continuous interdendritic network of eutectic carbides. These are observed even under rapid cooling, at rates as high as 106 K s-1. The main features of the as cast microstructure are the distribution and morphology of eutectic carbides, owing to their decisive influence on mechanical properties, and on the service performance of the high speed steels, even after hot working. Hence, the most important improvements on the as cast microstructure that have been obtained through progress in alloy design concern the type, morphology, and volume fraction of the eutectic carbides, while improvements obtained by progress in solidification processing are, on the other hand, mostly related to a significant reduction in the microstructure scale. The development of the microstructure in high speed steels through solidification is reviewed, emphasising the effects of the alloy chemical composition and of the cooling rate. The formation of the eutectic carbides and the techniques used to control their morphology and distribution, both under normal and rapid cooling, are discussed. Microstructures obtained through surface remelting and surface alloying using laser and electron beams are described, and the application of highly alloyed high speed steels to the manufacture of cast hot rolling mill rolls is reviewed.