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The eutectoid transformation of austenite can occur cooperatively (pearlite transformation) or by means of a non-cooperative mode (Divorced Eutectoid Transformation). In the cooperative mode, ferrite and cementite grow together, leading to the typical lamellar microstructure of pearlite. In the non-cooperative mode, spheroidal cementite particles grow directly from the undissolved carbides in the austenite phase. The transformation product is a fully spheroidized microstructure. In this study, the parameters promoting the occurrence of DET in a hypereutectoid steel (austenitization temperature, cooling rate, presence of proeutectoid cementite in the initial microstructure) were investigated. It is shown that low undercooling levels and a homogenous distribution of fine carbides in the austenite promote the DET over the lamellar transformation mode. The spheroidized microstructures produced by DET lead to larger ductilities comparing to those obtained by the lamellar transformation mode.

Using self-made electromagnetic centrifugal casting machine, optical microscopy (OM) and D/max2200pc X-ray diffraction, the solidification microstructure and phases of as-cast high speed steel(HSS) roll made by sand casting, centrifugal casting and electromagnetic centrifugal casting were investigated. The experiment results show that the phases of as-cast high speed steel (HSS) roll are alloy carbide (such as W2C, VC, Cr7C3), martensite and austenite. The centrifugal casting and electromagnetic centrifugal casting can apparently improve the solidification structure of HSS roll. With the increase of electromagnetic field intensity (B), the volume fraction of austenite in the HSS solidification structure increased obviously and eutectic ledeburite decreased, the secondary carbide precipitated from the austenite is more fine and distribution of secondary carbide is more even.

Based on an analytical one-dimensional model, austenite growth into pearlite lamella and the corresponding phase evolution during isothermal reverse transformation to austenite at 1000-1183 K in Fe-C fully pearlitic steels containing 0.6-1.0 mass% C (in the austenite single phase field of Fe-C phase diagram) were simulated. It was found that the rate of austenite growth into ferrite increases faster with increasing reversion temperature than into cementite. Three types of phase evolution dependent on reversion temperature and carbon content were classified: 1) cementite rather than ferrite disappears first; 2) ferrite and cementite simultaneously disappear; 3) ferrite rather than cementite disappears first. The type of phase evolution in a hypoeutectoid steel heated above its Ae3temperature possibly changes in the order of 1), 2) and 3) as the reversion temperature increases. For eutectoid and hypereutectoid steels, the phase evolution during isothermal reversion always obeys the type 3).

The isothermal and nonisothermal tempering of martensite in dual-phase (DP) steels was investigated mainly by analytical transmission electron microscopy, and the effect on softening behavior was studied. The isothermal tempering resulted in coarsening and spheroidization of cementite and complete recovery of laths. However, nonisothermal tempering manifested fine quasi-spherical intralath and platelike interlath cementite, decomposition of retained austenite, and partial recovery of laths. The distinct characteristic of nonisothermal tempering was primarily attributed to the synergistic effect of delay in cementite precipitation and insufficient time for diffusion of carbon due to rapid heating that delays the third stage of tempering. The finer size and platelike morphology of cementite coupled with partial recovery of lath resulted in reduced softening in nonisothermal tempering compared to severe softening in isothermal tempering due to large spheroidized cementite and complete recovery of lath substructure. The substitutional content of precipitated cementite in nonisothermal tempering was correlated to the richness of particular steel chemistry. Softening resistance during nonisothermal tempering was related to DP steel chemistry, i.e., Cr and Mn content. Fine cementite and less decomposed martensite in rich chemistry confer high resistance to softening compared to leaner chemistries, which indicated severe decomposition of martensite with coarser cementite.

Cementite spheroidization of GCr15 bearing steel includes granulating and growth of cementite. The effects of divorced eutectoid transformation (DET) temperatures on growth of cementite were studied. It was found that the particles of cementite are fine and uniform when DET occurs at 690～720°С, and alloy elements mostly precipitate at different temperatures during cementite growth of GCr15 bearing steel; Cr and Si mostly precipitate in the eutectoid temperature upper limit, while Mn is in the eutectoid temperature lower limit.

The effect of steplike high-temperature treatment (SHTT) on the composition and structure of carbides in the ledeburite eutectic of R6M5 high-speed steel ingots is studied. It is shown that SHTT processes lead to fragmentation and a change in the composition of the primary carbides, which causes their disintegration and a decrease in the carbide size during hot deformation.

Direct welding between spheroidal graphite cast iron (FCD700) and mild steel (SS400) was conducted using electron beam welding to study the microstructure and the mechanical properties of the welds.Results showed that one-pass welding yielded an over-hardened fusion zone exhibiting acicular martensite structure (815 HV) with cracks and porosities. Two-pass welding contained fewer porosities. Both one-pass and two-pass welding displayed acicular martensite and ledeburite within the microstructure of spheroidal graphite cast iron in heat-affected zone. The tensile strength of both one-pass and two-pass welded joints was lower than that of mild steel base metals. These joints ruptured at the fusion zone or the mild steel bond. However, two-pass welded joints demonstrated tensile yield stress values greater than or equal to those of mild steel base metals. Hardening of the fusion zone and the heat-affected zone of spheroidal graphite cast iron made the impact strength values of two-pass welded joints conspicuously lower than those of the spheroidal graphite cast iron base metal. The fatigue strength of two-pass welded joints almost equaled that of mild steel base metal, with a fatigue limit of 209 MPa.

The effect of silicon on the spheroidization of cementite in hypereutectoid high carbon chromium bearing steels has been investigated on the basis of microstructural analysis and thermodynamic calculations. The results showed that an increase of silicon content in high carbon chromium bearing steels retards the spheoridization of cementite. The thermodynamic calculations revealed that the shrinkage of the austenite phase field in bearing steels with increasing silicon content gave rise to an increase of volume fraction of cementite at an annealing temperature, possibly resulting in incomplete spheroidization. Furthermore, due to the low solubility of silicon in cementite, an increase of silicon content can raise the activity or chemical potential of carbon atoms in austenite at the austenite/cementite interfaces. Consequently, the difference in chemical potential of carbon atoms at the interfaces would be reduced with increasing silicon content, causing a decrease of the driving force for their diffusion from cementite to austenite.

In ductile cast irons with copper, cementite stability was investigated against an annealing heat treatment used to obtain a fully ferritic matrix. Copper controls cast-iron mechanical properties, but its role in the matrix microstructure formation remains unclear. Some reports suggest the copper layer around graphite or cementite. They can be barrier to carbon diffusion at eutectoid reaction, however it is difficult to understand the mechanism of pearlite stability by copper. To confirm the existence of the barrier and effect of copper addtion, ten 9-mm-thick spheroidal graphite cast iron castings were prepared with different copper contents of 0.16 wt% – 0.69 wt%. The samples’ as-cast microstructures included spheroidal graphite, ledeburite, and pearlite. The pearlite fraction degreases to about 10% by heat treatment for ordinary ductile irons without intentional copper addition. The samples’ copper content and the pearlite fraction after heat treatment are not linearly related. The retained pearlite increased suddenly with increased copper content greater than 0.4 wt%. However, even the sample with the highest copper content showed no precipitation of a copper solid solution around graphite nodule or cementite.

Information on the diffusional transformation products of austenite in high-carbon steels is reviewed and supplemented with new microscopic studies. A comparison with transformation products in low-carbon steels indicates that there is a symmetry with pearlite in the middle, where ferrite and cementite are equal partners, and with acicular ferrite or cementite on each side. They both form with a surface relief, and at lower temperatures, each one is the leading phase in a eutectoid microstructure, bainite and inverse bainite, respectively. However, there is an asymmetry because at low temperatures bainite appears in high-carbon steels but inverse bainite never appears in low-carbon steels. At a constant high carbon content, there is another kind of symmetry, which is related to temperature. At intermediate temperatures the eutectoid reaction results in spherical nodules in which the cementite constituent originates from Widmanstatten plates. It turns spiky at both higher and lower temperatures with the leading phase in the spikes being cementite at higher temperatures and ferrite at lower temperatures. In the first kind of symmetry, there is an abrupt change among the three reaction products; in the second kind of symmetry, there is a gradual change. Accepting that all the eutectoid microstructures form by diffusion of carbon, one may explain the existence of both symmetries by the variation of the ratio of the supersaturations of ferrite and cementite with carbon content and with temperature.

To improve the wear resistance of ductile cast iron, plasma beam remelt-solidified hardening on the surface is adopted. Scanning electron microscope and micro-hardness tester is used to analyze the microstructure and performance for plasma beam remelt-solidified layer of nodular cast iron. The results show that micromelted-solidified hardening of the nodular cast iron surface can be obtained when the operating current is up to 50A. Along with the operating current increases, the width and depth of remelt-solidified layer and hardened layer increase, but the hardness goes down. After the hardening, graphite phase in remelt-solidified region is vanishing. The microstructure of remelt-solidified region is tiny ledeburite and remained austenite and of transformation hardening region is acicular martensite, remained austenite，spheroid graphite and ferrite .In transition region, martensite shell around nodular graphite appears, which is advantageous to enhance the wear resistance. From the surface to inner, the microhardness declines first and then increases, after achieving the maximum value the hardness slowly drops. The highest microhardness appears at the second-surface layer which has a certain distance to the surface.

Multicarbide reinforced metal matrix composite (MMC) layers on a ductile iron (QT600-3) were fabricated by laser surface alloying (LSA) using two types of laser: a 5 kW continuous wave (CW) CO 2 laser and a 400 W pulsed Nd:YAG laser, respectively. The research indicated that LSA of the ductile iron with multicarbide reinforced MMC layers demonstrates sound alloying layers free of cracks and porosities. The microstructure, phase structure and wear properties of MMC layers were investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), as well as dry sliding wear testing. The microstructure of the alloyed layer is composed of pre-eutectic austenite, ledeburite, spherical TiC, Cr 7 C 3 and Cr 23 C 6 with various morphologies. TiC particles are dispersed uniformly in the upper region of MMC layers. The average hardness of LSA layers by CO 2 laser and pulsed Nd:YAG laser is 859 HV 0.2 and 727 HV 0.2 , respectively. The dry sliding wear testing shows the wear resistance of ductile iron is significantly improved after LSA with multicarbide.

To obtain new unconventional structures with specific mechanical and physical properties is possible not only by the development of new types of materials but also by treatment of conventional materials using unconventional innovative technological procedures. One of these technologies is the forming in semi-solid state involving rapid solidification of miniature components from steels. Production of such components is complicated by a number of technical problems. To explain phenomena of the process and structure development, the production of miniature components from the tool steel X210Cr12 difficult to form was experimentally tested. The structure of this originally ledeburite steel consisted of 95 % of metastable austenite after the treatment. Metastable austenite was located particularly in globular and polygonal grains while the remaining interspaces were filled by lamellar network. The detected high stability of extremely high fraction of metastable austenite was tested under different conditions of thermal exposition and mechanical loading.

This study investigates the effect of the cementite phase on the surface hardening of carbon steels when they are shot-peened. Three carbon steels were used in this study: 0.1% C, 0.45% C, and 0.8% C steels. The results show that the surface hardness after shot peening is proportional to its carbon content. Grains at the surface were transformed into grains with lamellar structures. The cementite was spheroidized by energy generated from the severe plastic deformation at the surface, the ferrite grain size was refined noticeably, and the carbon dissolved in the ferrite. The higher the carbon content in the ferrite, the higher the degree of grain refinement was observed. The primary reason for the noteworthy enhancement of surface hardening likely originates from both the grain refinement and supersaturation of the carbon in the ferrite following cementite dissolution.

The influence of silicon on the spheroidization of cementite in hypereutectoid 1.0C-1.45Cr bearing steels has been investigated, on the basis of microstructural analysis and thermodynamic calculations. The silicon content was varied 0.25 to 2.00 in weight percent. Annealed at 790∼850°C for 6 hr, the 0.25Si and 1.00Si steels were entirely spheroidized at 790°C, while 1.50Si and 2.00Si steels at 830°C, respectively. This implies that the increase of silicon content in hypereutectoid steels retards the spheoridization of cementite. The thermodynamic calculations revealed that silicon atoms were partitioned into not cementite but austenite at annealing temperatures, and the increase of silicon content can raise the chemical potential of carbon atoms within austenite at austenite/cementite interfaces, causing the decrease of driving force for the diffusion of carbon atoms from cementite to austenite.

The wear resistance, corrosion resistance, high temperature resistance layers were prepared on the surface of ductile iron via laser alloying process, using the mixed ponder of sub-micron carbides power as starting materials. The microstructures of the different laser alloying layers were characterized by XRD, SEM, EDS, TEM. The microhardness and wear resisitance of the laser alloying layers were examined. The results reveal that the flat alloyed coating combines metallurgically with the substrate. the laser area was composed by alloyed zone ,heat-affected zone and matrix zone. The alloyed zone was composed mainly by ledeburite and carbide, while martensite and retained austenite were contained in the heat affected zone, there is no significant change in the Matrix zone. Under conditions that the laser power, spot diameter remain unchanged, with in 400 ~ 1000 mm/min scanning speed, the hardness of alloyed coating increases with increasing scanning speed. The weightlessness of the alloyed samples under the dry sliding friction is one-sixteenth of ductile iron. The wear resisitance of the alloyed coating has improved significantly.

It is very important to understand interstitial carbon behaviors in cold rolled steel to get the good formability as well as the high strength. In low carbon steel, most of carbons are consumed by the formation of grain boundary cementite during cooling. During heating and holding between Ae1 and Ae3, cementite is dissolved and consequently carbon enriched austenite is formed. By controlled cooling, retained austenite as well as bainite and martensite are formed. In this study, the effect of silicon, intercritical annealing, isothermal bainite transformation on the formation of ferritic bainite, cementite and retained austenite are modeled by nucleation and growth, diffusion and dissolution. In addition, the formation of retained austenite and their carbon contents are modeled and compared with experimental data.

The effect of prior microstructures on the behavior of cementite particles in conjunction with microstructural changes of the matrix during subcritical annealing was investigated by changing the initial microstructures into ferrite + coarse pearlite, ferrite + fine pearlite, bainite, and martensite, in medium carbon steels. While the coarsening of cementite particles in martensite proceeded rapidly with the growth of large cementite particles at boundaries with the dissolution of smaller particles within martensite laths, the coarsening rate of cementite particles in bainite was found to be much slower than that in martensite. This could be attributed to the thermal stability of cementite particles, the smaller amount of carbon in solution, and the lower driving force for solute diffusion due to the uniform size distribution of cementite particles in bainite. The controlling coarsening kinetics in medium carbon steels with ferrite-pearlite, bainite and martensite, were found as boundary diffusion, diffusion along dislocation, a combination of boundary diffusion and diffusion along dislocation, respectively.

The effect of prior microstructures on mechanical properties in low carbon steels were examined by comparing the behavior of cementite and mechanical properties of cryo-rolled and subsequently annealed steels. Prior microstructures consisted of ferrite + pearlite, banite or martensite. Steels, consisting of bainitic microstructure, exhibited the better combination of strength - ductility than steels with other prior microstructures, such as ferrite + pearlite and martensite.

Erosive wear due to solid particle impingement is a very intensive degradation process of surface layers of metallic materials. Erosion resistance is influenced by the working conditions (impact angle, impact velocity of solid particles, size, shape, hardness and amount of impinging particles) and the parameters of the worn material like hardness and microstructure. In our experiments some structural and tool steels were tested by slurry with SiO 2 particles at a flow velocity of 20 m/s. The microstructures of the tested steels were modified in a broad range by changing the conditions of their heat treatment. Increasing pearlite share in the structure of annealed carbon and low-alloyed steels has a positive effect on their erosion resistance. The growing carbon content in the tested hardened steels increases their erosion resistance. Maximum erosion resistance was found in hardened chromium ledeburite steel. Hardened high-speed steel HS 11-0-4 in spite of its high hardness has lower erosion resistance than ledeburitic chomium steels. An increasing amount of retained austenite and decreasing carbide and martensite shares with growing quenching temperature of the tested ledeburitic chromium steels leads to the reduction of their erosion resistance.

The subject of the study is the high-carbon tool cast steel G200CrMoNi4-3-3 used for metallurgical rolls, especially in section rolling mills. The test material was derived from a roll damaged in production; therefore, the authors had the material in a raw state at their disposal, on which they were able to carry out additional heat treatment operations. The pearlitic matrix of casting steel G200CrMoNi4-3-3 allows machining to be done to modify the pass or to remove any defects, and the primary and secondary precipitates of carbides enhance the tribological properties. The authors have been for years involved in the optimization of the structure of this material by slight correction to its chemical composition and/or the modification of heat treatment. The presented principles of heat treatment modifications will lead to considerable economic and ecologic profits. It has also been demonstrated that raising slightly the contents of carbide-forming elements, which markedly increases the quantity of transformed ledeburite, results in an enhancement of tribological properties. The analysis of a dozen or so rolls exploited down to the dead roll diameter has shown that roll of cast steel with increased contents of carbon and carbide-forming elements exhibit better service properties, as characterized by the amount of feedstock rolled. Such a method of enhancing the service properties required the assessment of fracture toughness, which was verified using the linear-elastic methods of fracture mechanics.

A number of morphological features of pearlite were revealed through scanning electron microscopy using deeply etched specimens. These include cementite branching, bridging, gaps, holes and curvature. The presence of cementite thin films or networks along the austenite grain boundaries in eutectoid steel and at the interface between pearlite and proeutectoid ferrite in hypoeutectoid steel is another characteristic of pearlite. Further-more, ferrite thin films surrounding the proeutectoid cementite in hypereutectoid steels are also observed. Hence, it is considered that in hypoeutectoid steels the nucleus for pearlite is a film of cementite rather than the expected proeutectoid ferrite and, similarly, in hypereutectoid steels pearlite forms from a ferrite film rather than from proeutectoid cementite. Convergent beam Kikuchi line diffraction was used to accurately determine the orientation relationships between pearlitic constituents and parent austenite in a Hadfields steel. The results show that neither the pearlitic ferrite nor the cementite is crystallographically related to the austenite grain into which the pearlite was growing and to that into which it was not growing. in addition, a new orientation relationship between pearlitic cementite and ferrite in the Hadfield steel was also observed. It is: ((1) over bar 03)(Z)parallel to((1) over bar 01)(F) [010](Z)parallel to 131](F) [311](Z)8.5 degrees from [1 (1) over bar1](F)

In this study four irons were casted with different chromium and vanadium contents: 2.66% Cr, 5.01% Cr, 2.51% V and 5.19% V. Their microstructure is composed of: ledeburite, graphite and M3C carbides (cementite). Pin-abrasion tests were carried out using fixed alumina abrasive grains at different loads: 1, 2, 4.6 and 10 N. The wear surface and the abrasive paper were examined by scanning electron microscopy for identifying the wear micromechanism. The results reveal that the mass loss increased with the load increase, and the effect of the percentage of chromium on mass loss is inverted when the load is increased from 4.6 to 10 N; for 4.6 N the mass loss decreased when the chromium percentage was increased from 2.66% to 5.01%. Nevertheless, for 10 N the mass loss increased when the chromium percentage was increased. The worn surfaces of the materials tested at 1 N show microcutting caused by the abrasive tip that produces continuous microchips. The worn surfaces and the abrasive paper tested at 10 N show continuous microchips and brittle debris. The results show that high pressures produce a brittle wear mechanism and low pressures produce a more ductile wear micromechanism, for this, the applied pressure defines the dependence between the wear resistance and wear micromechanism.

The surface of nodular graphite cast iron samples was melted by 50% overlapping passes from a 3 kW CW CO 2 laser. The objective was to modify the microstructure and improve the hardness and erosion resistance of the surface. The results showed that laser melting led to complete dissolution of the graphite nodules which on solidifying created an inter-dendritic network of ledeburite eutectic with a very fine structure, good homogeneity, and high hardness. Sand particle erosion experiments were carried out at impingement angles of 30°, 60°, and 90° using angular particles of size between 300 and 600 μm. The velocity of the sand particles was 50 m/s, which was controlled by the gas pressure and measured by the double-disc method. The erosion resistance of the laser treated nodular cast iron was 110 times greater than the untreated material. The erosion mechanism of the untreated nodular cast iron under normal and oblique angles was by severe plastic deformation and ploughing; whilst the mechanism for the treated specimens was by fatigue cracking. The improvements of erosion resistance after laser treatment were considered due to the very fine structure, high micro hardness (650 Hv0.1) with the resistance to plastic flow and to the dissolution of the graphite nodules.

The electron backscattering diffraction technique was used to analyse the nature of carbides present in an ancient wootz steel blade. Bulky carbides, pro-eutectoid carbide along the prior austenite grain boundaries and fine spheroidized carbides were detected. Electron backscattering diffraction was employed to understand the texture of these carbides. The orientations of the cementite frequently occur in clusters, which points to a common origin of the members of the cluster. For the bands of coarse cementite, the origin is probably large coarse particles formed during the original cooling of the wootz cake. Pearlite formed earlier in the forging process has led to groups of similarly oriented fine cementite particles. The crystallographic texture of the cementite is sharp whereas that of the ferrite is weak. The sharp cementite textures point to the longevity of the coarse cementite throughout the repeated forging steps and to the influence of existing textured cementite on the nucleation of new cementite during cooling.

The present research identifies manufacturing factors that influence the metastable constituent in mottled Nihard cast irons. These irons constitute the roll shells of duplex work rolls processed by centrifugal casting. The research methodology employed a saturated design of experiments program with 7 factors, 8 experiments and a resolution of III. An increase from 6 to 10 kg/T of inoculated FeB enhanced metastable solidification by increasing the amount of ledeburite and the amount of cementite. Similarly, decreasing the Si content from 1.1 – 1.2 to 0.9 – 1.0 wt.% increased the amount of ledeburite and cementite. Finally, the use of casting machines without isolating sleeves increased the roll barrel hardness in the as-cast condition and after tempering.

Semi-solid M2 steel casting ingots were prepared using inclined slope pre-crystallization method, and the microstructure at different slope length and thermal plasticity of ingots were investigated in this paper. It was clarified that semi-solid processing technology can solve the serious problem of eutectic carbides segregation in casting microstructure. The dendritic primary austenite grains are changed into non-dentritic or equiaxed grains, and the eutectic ledeburite carbide networks are fine. So, it improves the thermal plasticity of casting ingots, and the carbide distribution of the semi-solid casting ingots is better than conventional casting after being forged.

Fe-based composite coatings reinforced by in situ synthesized particles have been produced by laser melting a precursor powder mixture of Fe-based alloy powder, Ti, Zr and C. The microstructure of the coating is typically hypo-eutectic, which consists of martensite, residual austenite, ledeburite and dispersed in situ carbide particles. The experimental results show that laser melting a precursor containing both Zr and Ti is favorable to form particles in the maximum volume fraction compared with those containing either of them. The particles are investigated to be multiple carbides.

In order to improve surface properties, high chromium austenitic base heat-resistant cast steel was scanned with a 5kW continuous wave CO2 laser, the specimen was aged at the temperature of 600°C~900°C. The microstructure and phase composition of the specimen were analysed with optical microscopy, electronic microscope and X-ray diffractionse. The hardness was measured. The results show that as-cast structure of high chromium cast steel is coarse and non-homogeneous, and mainly consist of austenite, ledeburite and carbides. After laser surface melting, the section is divided into the melted zone consisted of fine austenite and carbides, the heat affected zone composed of austenite and eutectic carbides, and the base meta1. The melted zone is very fine structures with dendritic crystals, only at the bottom a cellular structure is observed. A continuous carbide network is located in the austenitic grain boundaries at the heat affected zone. Carbides particles distribute dispersed out, the hardness of melted zone increases 35% than the base metal after aging. The area and the hardness of various zones are related to the laser processing parameters. The hardening depth of melted zone and heat affected zone may be up to 200μm~300μm.

In order to enhance thermal fatigue resistance of gray cast iron with non-smooth surface further, researches on laser alloying of Cr powder with different scanning speed were performed to change both the composition and microstructure of non-smooth unit. The results indicated that there was an optimal scanning speed (2 mm/s) which can contribute maximal Cr element in alloyed zone, and increasing laser scanning speed resulted in smaller non-smooth unit and more pores in it. The microstructure in alloyed layer was composed of pre-eutectic phases, ledeburite eutectic and chromium carbides of Cr 23 C 6 . Thermal fatigue resistance of non-smooth sample is better than that of smooth sample, and among non-smooth samples, sample treated by laser Cr alloying has superior resistance to thermal fatigue compared with laser melting treated sample, in addition, the resistance of laser alloying non-smooth samples increases with scanning speed slowing.

In the present paper, the results of a fractional design of experiments (DOE) with 16 experiments for 7 factors and resolution IV are presented. The goal was to identify the active roll manufacturing factors that influence roll barrel hardness after a double tempering treatment, the primary austenite grain size and its volume fraction, and the volume fraction of ledeburite in the outer ring layer of duplex work rolls made of Nihard cast iron. As a primary conclusion, both the total Si percentage and the amount of SiCaMn inoculant added to the ladle were found to have a significant effect on the volume fraction of ledeburite. The statistical analysis also showed that high Si percentages and heavier ring roll layer weights were the significant factors promoting the increase in the size of the gamma grains. High Si contents present in the melt and the addition of SiCaMn as inoculant seem to have a counter effect whereby the volume fraction of stable eutectic gamma increases and the volume fraction of proeutectic gamma decreases, with a positive balance for the sum of these austenites of different origins. Finally, the factors that have an influence on roll barrel hardness are those factors that promote the chill effect, such as low Si content, small amounts of liquid being poured into the mould to build up the outer ring layer, and the use of moulds without insulating sleeves.

Microstructures of cold drawn pearlitic steel wires were investigated by three-dimensional atom probe (3D-AP) to understand the influence of alloying elements on the decomposition of cementite. Before cold drawing, Si is mostly located in the ferrite phase, while Cr is located in the Fe3C phase and the amount of Mn is similar in Fe3C and in ferrite. Higher Si amount leads to higher dissolution rate of cementite and Cr has a little effect on cementite decomposition during drawing.

A new type of wear resistant low carbon Fe–B cast steel with granular borides can be obtained by alloying with titanium and cerium rare earth (RE). As a result, the as-cast eutectic boride structures of Fe–B cast steel are greatly refined and a blocky, less interconnected boride network is obtained from continuous ledeburite. After heat treatment, the boride eutectic in the modified Fe–B cast steel is in the form of a granular boride structure that appears to be isolated particles The guide rollers made of modified low carbon Fe–B cast steel show excellent wear resistance and thermal fatigue resistance in high speed wire mills.

This research tries to improve the plasma surface W, Mo alloying process by adding inlet methane aside from the original inert gas argon. The carbon and hydrogen particles are incorporated into the ion sputtering, ionization, surface activation and diffusion processes. The W, Mo atoms sputtered from the target diffuse into the surface of the substrate at the same time with the diffusion of carbon atoms. So the synergism of the alloying process and the carburizing process is established in this way. The hydrogen atoms participate the reduction and activation process on the surface of the target and the substrate. The surface HSS combines with substrate via metallurgical bonding and the carbides are all secondary carbides formed at lower temperature during solid state diffusion. These carbides are very soluble to the austenite. This makes the alloy elements fully functional. The carbides with granular shape and distributes homogeneously on the matrix are very fine. No coarse ledeburite eutectic carbide exists. After the co-alloying process of W, Mo, C, direct quench or quench at lower temperature can be applied.

Cr-Mo diffusion layer on carbon steels was prepared by double glow plasma surface metallurgy and treated by ultra-saturated carbonization, quenching and tempering, the excellent wear resistance was obtained. The results indicated that the hardness of surface alloying was up to 1300 Hv 0.025 . The carbides in the alloyed layer were fine and dispersed without coarse eutectic ledeburite. The microstructure of the composite layer indicated that the dimension of surface carbides was less 1μm. The abrasion experimental results showed that the average relative wear resistance of modified-steels was 10.3 times as that of T10 steel by quenching and low tempering. The alloy layer possessed a very strong ability resistance to tempering, and its surface hardness exceeds 595 Hv 0.025 after tempering at 690°C for 4h.

Mo-Cr diffusion layer on carbon steels are prepared by double glow plasma surface metallurgy and then treated by ultra-saturated carbonization, quenching and tempering. The content of component is roughly that of high-speed steels (HSS). The results showed that the depth of coating is over 100μm and the content of Mo, Cr alloyed layer is about 20% and 10% respectively. Surface carbon content is over 2.0% after ultra-saturated carbonization. The carbides of the alloyed layer are fine and dispersed, without coarse eutectic ledeburite. X-ray diffraction showed that the carbides are M6C, M2C, M23C6 etc. SEM analyse indicated that the dimension of surface carbide is less 1μm. The abrasion experimental results showed that the relative wear resistance of the treated sample was 2.38 times as that of quenched GCr15.

The first step in the heat-treatment processes for a vast majority of commercial steels is austenitization. There is much less research put in this field comparing to the cooling transformation, but the interest is continuously increasing especially in view of the development of TRIP and Dual-phase steels. The microstructural evolution during continuous heating experiments has been studied for a series of C-Mn steels with carbon contents in the range 0.35-0.45 wt. % using optical and scanning electron (SEM) microscopy. It is shown that the formation of the austenitic phase is possible in pearlitic as well as in ferritic regions, although in the former it proceeds at a much faster rate due to the shorter diffusion distances. Thus a considerable overlap in time of the ferriteto- austenite and the pearlite-to-austenite transformations is likely to occur. Another observation that was made during the experiments is that depending on the heating rate, the pearlite-to-austenite transformation can proceed in either one or two steps. At low heating rates (0.05 °C/s) ferrite and cementite plates transform simultaneously. At higher heating rates (20 °C/s) it is a two-step process: first ferrite transforms to austenite within pearlite grains and then the dissolution of the cementite lamellae takes place.

The paper deals with microstructure and phase analysis of bulk samples from Cr–Mo–V tool steel of ledeburite type deeply undercooled by the electromagnetic levitation method and subsequently solidified. In quasi-equilibrium conditions, solidification of investigated steel starts by austenite formation and it is finished by eutectic reactions resulting in the development of morphologically different M 4 C 3 and M 7 C 3 carbides which are located in the interdendritic positions. During levitation experiments the melt undercoolings from 50 °C to 290 °C below equilibrium liquidus temperature were achieved. In the deeply undercooled and spontaneously solidified samples, grain refined microstructures and carbide phases of the M 7 C 3 , M 4 C 3 and M 23 C 6 types were observed. Carbide phases were located at the grain boundaries of the metastable austenite as eutectic colonies and carbide skeletons. Based on the morphological features, it is proposed that grain refined microstructures were created by dendrite fragmentation after recalescence. Moreover, relatively small carbide phases were detected inside the austenite grains. It is supposed that these carbide phases in austenite grains are formed during postrecalescence stage of solidification from austenite supersaturated by carbon and carbide forming elements.

Microstructures formed by degenerate pearlite transformation in an Fe-0.38mass%C alloy were studied by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Degenerate pearlite which contains fine cementite particles even at the growth front was observed with other structures such as proeutectoid ferrite, lamellar pearlite and bainite in a temperature range between 773K and 923K. As the isothermal transformation temperature is lowered, a fraction of the degenerate pearlite increases. The degenerate pearlite consists of ‘block’ (a region in which ferrite orientations are nearly the same) and ‘colony’ (a region containing cementite particles of nearly the same orientation), both of which are similar to those in lamellar pearlite. Block boundaries within an austenite grain are generally of high-angle type and their misorientations deviate largely from intervariant relationships for the K-S orientation relationship. In contrast, colony boundaries are of low-angle type. Cementite films are formed along those ferrite boundaries in the degenerate pearlite, presumably formed by encounter of the blocks or colonies.

The precipitation behavior of cementite in low carbon steels at various heating rates from 0.3 to 100 K/s has been studied using a high-frequency induction heating apparatus. The materials used in this study were steel platesfor welded structures: 610 and 780 MPa class steel plates with a mixed microstructure of bainite and martensite.Cementite was observed using a carbon extraction replica method and the hardness and toughness were also examined. When heated at the conventional slow rate of 0.3 K/s, relatively large cementite particles with an average diameter of 72 nm precipitated at the lath boundaries, whereas when heated at a rapid rate over 3.0 K/s, cementite precipitated both within the laths and at the lath boundaries, and the cementite was refined down to an average diameter of 54 nm. With such refinement of the cementite, the toughness was improved. On the other hand, the hardness was irrespective of the heating rate and was dependent on the tempering parameter. TEM observations of the cementite precipitation behavior during the rapid heating process revealed that cementite begins to precipitate at the lath boundaries at about 773 K and within the laths at about 873 K. It is concluded that rapid heating especially from 773 to 873 K contributes to the cementite refinement and consequently the improvement in toughness. The effect of alloying elements such as chromium, molybdenum or silicon on the cementite growth during the rapid heating and tempering treatment is also discussed.

Examination method of duplex stainless steel is considered as study case, and TRIZ contradiction matrix theory, 40 inventive principles and substance-field model are synthetically utilized to solve examination problems. Methods of two-phase microstructure examination of duplex stainless steel with TRIZ methods are analyzed. Finally the practical application of TRIZ and the superiority of TRIZ theory are validated. Introduction To research the relationship among component, structure and property is one of the important missions of the physical metallurgy. And the depth of research depended on the capacity of identification of the inner structure of the metallic material. Therefore metallographic examination is one of the most important segments in the field of metallic material science. On research or application of metallic material, there are two important aspects. First, the result of the structure and the property of metallic material depended on the component. If it is going to be improved, lots of physical and chemical inspections have to be done. Second, the relation and changing laws among component, structure and property are proved by large amount of physical and chemical inspection too. Therefore the metallographic examination is very significant and useful in the above aspects. In conclusion, in the field of research or application of metallic material, metallographic examination is very necessary. Liu proposed a new method about examination on the heterogeneity of ledeburite eutectic carbide. This new method tried to increase efficiency and streamline the examination processes. E. Schaberger tried to use the electrolysis etching method to make the electrolyte for aluminum alloy-Barker 70 use in the die casting magnesium alloy-AZ91HP. And it was success in revealing the colorful grains and the dendritic crystal inside the grains. Yuan described the metallographic examination key point of the 18-10 stainless steel. Obviously, methods in this field are mainly based on the experiences and some traditional methods such as brainstorming method or trial-and-error method. TRIZ theory is not widely used in this territory. Case Study Microscopic metallographic examination and analysis are the important methods to study the inner structure of metallic material. By measuring the 2D metallographic phase, the 3D morphology can be calculated and confirmed. After that, the relationship among alloying component, micro structure and mechanical property can be built. And it can provide the reliable data for the estimate and usage of the metallic material. In general, microscope is the most common instrument for microscopic metallographic examination. By this instrument, the treated specimen will be observed. For different material, different micro structure will be found inside the microscope. By observing the metallographic phase, the research and analysis for the metallic material can be carried out. In the past, most analysis on metallographic examination is qualitative analysis. It is said that people can only judge the component phases of the metallic material but cannot judge the quantity of each phase. Usually people make the judgment by their theoretical knowledge and working experience. For example, Fig.1 and Fig.2 were from different materials, one is iron and the other is International Conference on Information Sciences, Machinery, Materials and Energy (ICISMME 2015) © 2015. The authors Published by Atlantis Press 472 stainless steel. But they are very similar. Fig.1 is the iron metallographic photo and Fig.2 is the stainless steel metallographic photo, and there is one phase in Fig.1 but two in Fig.2. For the iron, 99% of the structure is the ferrite, it is no need to study the content of iron. But for the stainless steel, there are two phase inside (ferrite and austenite), and the proportion of each part will affect the property of the material obviously. Therefore it is necessary to study and tell the content of each phase in the field of stainless steel. But if we have these black and white photos only, boundary of ferrite and austenite can be seen and ferrite and austenite can be told. But what the proportion of each one will be a big problem and it seem to be a very tough. Fig.1 Metallographic Photo of Iron Fig.2 Metallographic Photo of Stainless Steel Solution of TRIZ If the problem is considered to be a Su-Field model, then transfer the specific problem into the Su-Field model problem is the first step. The procedures are as follow[4,5]: 1) Identify the component of the Su-Field model. According to the above case and the TRIZ theory, the metallographic phase, eyes and visual field are identified to the S1, S2 and F1. 2) Build Su-Field model In this case, the key point is that boundary of the ferrite and austenite can be seen but these two phases cannot be told and the quantities of each one cannot be calculated. To solve this problem with TRIZ method, we can build the sketch map of Su-Field model as shown in Fig.3. In this case, three components of the Su-Field are all complete, but the interaction of them is not efficient enough. This situation belongs to Type 4 of the general solution of the Su-Field (Insufficiency model). Fig.3 Su-Field model 3) Confirm the general solution of Su-Field model According to the general solution of the Su-Field model type 4, the second field should be added to reinforce the useful effect. Su-Field model is as shown in Fig.4. Then the suitable field for this model should be selected. Usually there are many fields can be selected, such as gravitational field, electromagnetic field, nuclear field, mechanical field, chemical field, and heat field. For this case, tell the difference between ferrite and austenite, and confirm the quantities of each phase are the final objective. But base on the black and white metallographic photos, it is difficult to tell the ferrite and Visual Field

Introduced in this article is the technique to acquire a high performance strengthened layer on carbon steel samples, namely, plasma alloying on the surface of Q235 steel and heat treatment technology. With this technique the alloying elements of Mo, Cr, and C can be obtained on the surface of Q235 steel samples. The content of the constituent elements is approximately up to high speed steels (HSS). The surface property required for the HSS after hardening and low tempering is attained. In the test, the alloying elements Mo and Cr were penetrated into the Q235 steel samples by glow discharge sputtering so that the content of the alloyed layer on the surface of the Q235 steel samples was about 20% Mo and 10% Cr. Two kinds of experiments were conducted. One was to carry out ultra-saturated carburization. The alloyed layer's composition was similar to molybdenum HSS with surface carburizing of more than 2.0%. The carbides of the alloyed layer were compact, uniform and disperse without a coarse eutectic ledeburite structure. The another was ion nitriding after the alloying elements of Mo and Cr were penetrated. The first process included hardening with low tempering and hardening with cryogenic treatment for 2 hr and low tempering. The second one was ion nitriding only. It was found that the surface hardness after cryogenic treatment is up to 1600 HV, much higher than that without cryogenic treatment. The abrasion test results indicate that, without the penetrated alloy elements Mo and Cr and without cryogenic treatment and ion nitriding, the friction coefficient is lower by one order of magnitude. The change in relative resistance is similar to the change in the friction coefficient, but without a proportional relationship.

To reduce the mixed fuel induced excessive wear of the cast iron engine cylinder liners, research on laser alloying of NiCr alloy with powder feeding was performed to locally change both the composition and the microstructure of the liner. The research indicated that laser alloying of 75Ni25Cr on grey cast iron liner demonstrates sound alloying layers free of cracks and porosities. The microstructure of the alloyed layer is composed of pre-eutectic austenite and ledeburite. The alloying element Ni is mainly located in the austenite, while Cr is mainly in cementite. The average hardness is HV 0.2 500. The corrosion resistance of the alloyed layers in diluted H 2 SO 4 solution and NaOH solution is dramatically improved compared to the grey cast iron. The relative wear resistance of the laser-alloyed 75Ni25Cr layer is 4.34 times of that of the grey cast iron. The improvements on the corrosion and wear resistance of the cast iron are attributed to the composition and microstructure change by laser alloying of 75Ni25Cr. Laser alloying can be a good solution to improve wear and corrosion resistance of the grey iron liners in mixed fuel environment.

Characteristic grain growth Occurred coincident with the Ostwald ripening of cementite particles upon annealing in a submicron-grained ferrite/cementite steel. The predictive capability of the Hall-Petch relation between the hardness and average ferrite size was demonstrated, independent of the distribution and size of cementite particles. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Eutectic polyhedration of the diagram is presented and special features of structure formation in high-manganese irons are analyzed. It is shown that eutectics of two kinds (alloyed ledeburite and a eutectic based on M7C3 carbides), which are in peritectic equilibrium with the melt, can be formed and be accompanied by a special austenite-carbide component having a pearlite-like structure. The quasi-eutectic and the M7C3-bearing eutectic in heat-treated high-manganese irons have a special morphology with composite arrangement of carbides in austenite. It is shown that additional alloying of manganese irons with silicon might be a promising direction. Silicon stabilizes the M7C3 carbide in its competition with cementite and ensures the possibility of fabricating austenitic mottles with such carbide. Mottles alloyed with manganese and silicon and having globular graphite, M7C3 carbides and metastable austenitic matrix are characterized by high wear resistance, good antifriction properties, and a combination of high mechanical properties.

Dissolution behavior of cementite in eutectoid steels with pearlitic and spheroidite structures by severe plastic deformation was studied. Applying a long time milling, cementite dissolved completely and matrix turned out to be nanocrystalline ferrite. By a ball drop deformation (at high strain rates), heavily deformed layers in which cementite dissolves completely or partially were produced. By applying pulsed laser irradiation, re-austenitized zone which transformed to fresh martensite during quenching was produced. The boundary between the re-austenitized zone and matrix exhibited similar microstructure with that observed in specimens subjected to a ball drop deformation. It was suggested that the dissolution of cementite by heavy deformation at high strain rates are probably due to thermal effect, that is, re-austenitization.

Neutron diffraction measurements have revealed that cementite peaks disappear in a pearlite steel with drawing and that the residual intergranular stresses are generated. The diffraction profiles in a heavily drawn specimen suggest the tetoragonality with a small c/a in the ferrite matrix. Although cementite was hardly observed in the heavily drawn specimen, its c/a value determined by neutron diffraction and mechanical behavior are quite different from those of as-quenched martensite. The changes in hardness and c/a with annealing or tempering were also different between heavily drawn pearlite and marteniste. Hence, most of carbon atoms do not exist inside the ferrite lattice in the drawn pearlite and multi-scaled heterogeneous plastic deformation in pearlite seems to affect the asymmetry in the diffraction profile. Fracture behavior and hardness change with tempering is different in the two microstructures.

The formation and homogenization of austenite from ferrite and pearlite are directly observed in the heat affected zone of a 1045 C–Mn steel arc weld. With rapid heating, cementite does not completely dissolve before the base metal ferrite is transformed, and a second austenite constituent forms. These two austenite constituents exist up to 1400 °C before a single homogeneous austenite phase is produced.

In this work, we studied the wear behavior of a low-Cr white cast iron (WCI) modified with ferrotitanium-rare earths-bismuth (Fe-Ti-RE-Bi) up to 2%. These additions modified the eutectic carbide structure of the alloy from continuous ledeburite into a blocky, less interconnected carbide network. The modified structure was wear tested under pure sliding conditions against a hardened M2 steel counter-face using a load of 250 N. It was observed that wear resistance increased as the modifier admixture increased. The modified structure had smaller more isolated carbides than the WCI with no Fe-Ti-RE-Bi additions. It was observed that large carbides fracture during sliding, which destabilizes the structure and causes degradation in the wear behavior. A transition from abrasive to oxidative wear after 20 km sliding occurred for all alloys. In addition, the modified alloys exhibited higher values of hardness and fracture toughness. These results are discussed in terms of the modified eutectic carbide microstructure.