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Bimetallic castings are widely employed as working elements in winning machines which work in conditions of intensive friction wear. The main features of wear are: dynamic percussive loads, intensive abrasive wear caused by erosion and corrosion. Three cylindrical rods cavities of the same dimensions of φ 20x200 mm were made in sand mould. Different amount of liquid iron alloy with carbon equivalent of 4.14, Mn of 0.58 and Cu of 0.17 wt% was poured into the three rod cylindrical cavities over the solid 304 stainless steels cylindrical desks inserts. Good coherent interfaces for all liquid/Solid volumes (16 to 24) are produced and multi-layers interfacial microstructure bimetal are produced. Increasing the liquid/solid volumes from 16 to 24 increases the thickness of transient layer from 52 to 89 μm and decreases the amount of ledeburite in the structure of solidified gray cast iron.

The spherical casting WC powder is a kind of new potential wear-resistance ceramic material. In this paper, its chemical composition, surface morphology, microstructure, phase, microhardness and some powder characteristics were investigated, and then the powders were applied in laser surface alloying treatment on medium carbon steel. The results indicate that the spherical WC powder consists of (wt.%) 94.06 W, 4.03 C and 1.91 other elements including Fe, V, Cr and Nb. Most of powder particles have regular spherical shape and smooth surface, and the microstructure is acicular eutectic of WC and W2C, which leads to high microhardness of 2812 HV. The fluidity of powders is 5.97 s/50g, and the apparent density of powders is 10.1 g/cm3. The laser alloyed layer is characterized by dendritic primary phase, ledeburite microstructure and some residual WC particles. The laser surface alloying treatment with adding material of spherical casting WC powder can enhanc the abrasive wear resistance of medium carbon steel by over 200%.

The ledeburite carbides segregated seriously in solidification of Cr12 tool steels and the morphology is distributed in banding with fishbone shapes resulting in low toughness. Thus the tools are usually failure with tipping, fracture and collapse in services. A new high strength and high toughness tool steel was developed to adapt for the requirement of high strength materials forming. The thermodynamic theory and equilibrium principle of carbon as well as computer aided optimizing design are used in.

The detailed mechanism of divorced pearlite in bearing steels began to be actively discussed more recently. The survey of divorced pearlite in higher Mn bearing steel was carried out through scanning electronic microscope following isothermal transformation heat treatment. The results show that while divorced transformation taking place in the higher Mn bearing steel just slightly below A1, the cementite could be produced in such way as growing on the base of pre-existing cementite particles in austenite, or emerge either in globular particles or in short rod directly from the austenite. Under isothermal transformation, the carbon atoms in austenite prefer to precipitate on the original boundary of the austenite. The enough small size of the cementite particles remained in the austenite is helpful for getting spheroidal cementite particles structure through divorced eutectoid transformation.

Die-casting plunger often fails due to serious wear on its cylindrical surface. The scrap of plunger used in large die-casting machine results in waste of materials and energy sources, and it is also against environmental protection. Therefore, the laser remanufacturing of die-casting plunger was studied in this paper. Both of the size and the performance of plungers were repaired by laser cladding surface modification using an iron-based self-fluxing alloy. The interface between original failed plunger and laser cladding layer showed a good metallurgical bond. The average thickness of laser cladding layer was 0.845 mm, and the average micro-hardness reached to 750 HV upwards. Microstructure in laser cladding layer was composed by the dendrite primary phase and the ledeburite organization. Iron (Fe), Chromium (Cr) and Molybdenum (Mo) elements were the main chemical compositions measured in laser cladding layer. The service life of laser remanufacturing plunger was nearly the same as the life of new plunger. However, its remanufacturing cost was only 50% of the new plunger’s. The laser remanufacturing technique is worth for extending and applying due to high cost performance.

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.

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.

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.

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.