Papers by Keyword: H13 Steel

Abstract: This paper introduces the principle of PACVD coating technology, technical characteristics, equipment composition and material characteristics of CrN+DLC. Taking H13 steel as the research object, its surface was treated with CrN+DLC. The microstructure, bonding state and hardness of the interface were studied by means of metallography, SEM, hardness and component distribution of the surface layer. The anti-crack ability and grade of DLC layer were analyzed by studying the shape of crack distribution with Rockwell hardness indentation, and the high quality layer with crack grade of HF1 was obtained. With the dual properties of diamond and graphite of DLC, it can make the die surface have lower friction coefficient, higher hardness, higher impact toughness, better solid lubrication performance and higher corrosion resistance. Surface DLC coating technology provides a new solution to improve the performance of the die.

Abstract: In order to improve the wear resistance of H13 steel, a layer of cobalt-based cladding layer was deposited on the surface of H13 steel by plasma transfer arc welding technology. High-temperature wear test was carried out on H13 steel and cladding layer under 300N loading force, and the two materials were ground at different temperatures with 300M steel. The experimental results show that under 300N loading force, the wear resistance of the cladding layer and H13 steel decreases first and then increases with the increase of temperature, which is related to the softening and oxidation of the material. At 350°C,the material softens and the oxide layer fails to entirely cover the wear surface, so the wear resistance of the cladding layer and H13 steel is lowered. At 500°C and 650°C, the wear surface is covered by a dense oxide layer, which protects the surface of the material from direct wear. The higher the temperature is, the thicker the oxide layer is and the better the protection effect is. At various experimental temperature, the wear resistance of the cladding layer is better than that of H13 steel. The surfacing of a cobalt-based cladding layer on the surface of H13 can improve the wear resistance of H13 steel.

Abstract: The recent development of study on H13 hot-work die steel is reported in this paper. Microstructures and mechanical properties and their changes with some factors are briefly introduced. The factors are included in melting, heat treatment, surface treatment, and so on.

Abstract: FeCrAl coating was prepared on the surface of H13 steel through electric arc spraying (EASP) technology. The surface and cross section morphology, elements and phase composition of the composite coating were analyzed by the means of scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The aluminum corrosion resistance was tested by the static hot-dip aluminum method in molten AC4C aluminum at 700°C. The result showed that the FeCrAl coating, of which the microstructure was compact, had typical layer structure, and a small amount of oxide films and pores could be found among the lamellar particles. FeCrAl coating mainly contained Fe-Cr solid solution and small amounts of Al₂O₃. The weight of H13 corrosion was 3 times as much as that of FeCrAl coating corrosion after static melting treatment for 1h, and the corrosion rate of H13 steel and FeCrAl coating were both increased as the corrosion time increased from 1h to 3h. It was worthy noted that the weight of H13 corrosion was significantly increased, which was 17 times as much as that of FeCrAl coating corrosion.

Abstract: The failure analysis of the H13 steel hot-forging mould is the main content in the open experiment. The scan electronic microscope and the optical microscope are used to analyze the failure workpiece in this experiment. The over-high quenching temperature, the too low drawing temperature, the insufficient drawing time and frequency, the over-high hardness value are the main reasons of fracture failure of the mould. The work environment of the failure materials, the heat treatment processing, the metallographic analysis, the fracture analysis and the using of test standard are the important aspects which the students should know. The students can learn how to analyze problem and how to solve them from the open experiments which is a good teaching try.

Abstract: Commercial hot extrusion is a billet-by-billet cyclic process, with high thermal and mechanical stresses generated in the die set. The die is a costly piece of equipment, and its long service life is essential for profitable operation. Extrusion dies primarily fail by fracture, wear, and plastic deformation. To avoid early failure, it is essential to have an optimum combination of toughness and hardness in the die. This combination can be achieved through a judicious mix of heat treatment and surface hardening. Experiments were conducted to determine mechanical properties of H13 steel after various heat treatment sequences. Heat treatment strategy is described in detail, and effect of different tempering temperatures on fracture toughness and hardness of the tool steel is reported. Changes in mechanical properties are also related to the variation in microstructure. For use in commercial hot extrusion dies, optimum tempering temperature for H13 steel was found to be near 525-600oC, for the best combination of toughness and hardness.

Abstract: In the present research, an attempt has been made to experimentally investigate the cutting forces in hard milling of H13 steel with coated carbide tools under dry, MQL (minimum quantity lubrication) and MQCL (minimum quantity cooling lubrication) cutting conditions. Based on Taguchis method, four-factor (cutting speed, feed per tooth, radial depth of cut, and axial depth of cut) four-level orthogonal experiments were employed. It is found that the periodical fluctuation of the cutting forces caused by the variation of the undeformed chip thickness with the entry/exit of the cutting edge is an essential feature of the hard milling process. The empirical models for cutting forces are established, and ANOVA (analysis of variance) indicates that the quadratic models can well express the relationship between cutting forces and cutting parameters.

Abstract: CrTiAlN hard coatings have been deposited on H13 steel for improving the oxidation resistance by Closed Field Unbalanced Magnetron Sputter Ion Plating (CFUMSIP). The phase components, surface and section morphology of H13 steel before and after oxidation were analyzed by XRD and SEM. The results showed that the columnar crystal film possesses three major parts, i.e., the internal Cr bonding layer, the intermediate CrN transition layer, the external CrTiAlN gradient coating. The selective oxidation of Cr element was found on the surface of uncoated H13 steel while oxidation, but a continuous protective layer was not formed because of low Cr content, finally a lot of alpha Fe₂O₃ particles took place on the surface of H13 steel owing to the oxidation of the matrix element. O element can diffuse much more easily through the coating and oxide scales at 800 °C, and spallation and cracks were not found during the oxidation. These results indicated that the CrTiAlN coating have excellent high-temperature oxidation resistance at 800 °C.

Abstract: H13 steel specimens with vapor oxidation surface treatment and without surface treatment, were carried out by thermal fatigue test and melting-loss test to research the effect of vapor oxidation surface treatment in the aluminum alloy die casting. The results show that the vapor-oxidized specimens have better erosion resistance and similar thermal fatigue resistance to those without surface treatment. Compound layer and compact layer form in melting-loss test are mainly Fe₂Si₂Al₈ and Fe₂Al₅, respectively.

Abstract: High-energy shot-peening on H13 steel after quenched. The samples with or without high-energy shot-peening were ion-nitrided at 520°C for 3h．The Microstructure，nitriding depth, hardness gradient, surface phase and Corrosion resistance of the nitride layers were compared between the high-energy shot-peening samples and the original samples using optical microscope, micro-hardness tester, X-ray diffraction and CH1660A electrochemical test. Results show that the high-energy shot-peening greatly speeds up the nitriding on the H13 steel at 520°C for 3h.. The depth of ion-nitriding layer after shot peening is from 0.11mm to 0.16mm, micro-hardness of the surface layer is from 998HV0.5 to 1105HV0.5, The hardness gradient is slightly flat . Phase structure and content of the surface is different by Powerful shot-peening and not. Corrosion resistance of the samples by high-energy shot-peening is significantly improved because it is easier to form a stable passive film.