Increase of Durability of Austenitic Steel by Overlap of Carburization and Diffusion Saturation from Liquid Metal Medium Solutions Technologies

This paper investigated the overlap of carburization and diffusion saturation from liquid metal medium solutions technologies. The carburization of austhenic steel able to increase of its wear resistance and microhardness to 700HV. But this kind of treatment provided to reduction of corrosion resistance. This effect conditioned by formation of chromium carbides, herewith austenite of steel impoverished of chromium. This paper proposes the new technology lets increase the durability of asthenic steels, using carburization and diffusion saturation in eutectic Pb-Bi-Li medium with adding of nickel and chromium. The most effective technology consisted of previous carburization, diffusion saturation and final carburization. First carburization provided to increase of surface layers microhardness to 2800 MPa, diffusion saturation to 7500 MPa, the final carburization to 19500 MPa. The properties of coating depended of combination of technological impact and technological modes of every stage of technological process: temperature and duration. The temperature influenced to microhardness of coating: when the temperature increased microhardness decreased. The duration of diffusion saturation influenced to thickness of diffusion layer: when the duration increased the thickness increased too

Investigation of the Surface Properties and Wear Properties of AISI H11 Steel Treated by Auxiliary Heating Plasma Nitriding

This paper presents an auxiliary heating method to maintain a uniform specimen temperature and precisely control nitriding temperature during plasma nitriding. The surface properties and wear properties of AISI H11 steel treated by auxiliary heating plasma nitriding are investigated. Firstly, the specimens with different diffusion layers and different hardness levels are fabricated through changing the plasma nitriding temperature. Secondly, the surface properties of the plasma-nitrided H11 steel specimens are characterized by a scanning electron microscope (SEM), X-ray diffractometer, metallographic microscope and microhardness tester. The results show that the surface hardness of the plasma-nitrided specimen is almost twice as high as that of the untreated specimen. The thickness of diffusion layer increases with the increase of nitriding temperature. However, the surface hardness firstly increases and then decreases with the increase of the nitriding temperature. Finally, the wear properties of untreated and plasma-nitrided H11 steel specimens are investigated under different friction conditions. The results show that the plasma-nitriding method can significantly improve the wear resistance of AISI H11 steel. The friction coefficient fluctuations of the plasma-nitrided specimens are all lower than those of the untreated specimens. In addition, the wear rates of the plasma-nitrided specimens rise along with load, and reduce along with the sliding speed and friction temperature.

Characterization of Urban Particulate Matter by Diffusive Gradients in Thin Film Technique

A diffusive gradient in thin films (DGT) technique was employed in characterization of the particulate matter related to the urban area suffering from heavy traffic. Kinetics of mobilization metals fluxes from the metal-contaminated particulate matter was investigated. To monitor responses of the particulate matter sample, DGT probes of various thickness of diffusion layer were deployed in aqueous model suspensions of the particulate matter for different time periods. Particulate matter samples and exposed DGT resin gels were decomposed in a mixture of nitric and hydrochloric acid in a microwave pressurized PTFE-lined system. Total content of some traffic-related elements (Cd, Co, Cu, Mo, Ni, Pb, Pd, Pt, Rh, Sb, and V) was determined by inductively coupled plasma mass spectrometry. DGT measurements revealed that two metals pools associated with particles could be recognized, which can be characterized as high soluble fraction and almost insoluble fraction. DGT-measured metal fluxes from the labile pool showed significant difference in mobilization and resupply fluxes of individual selected elements, which might reflect the origin of selected metals and their speciation in particulate matter. The DGT technique can be applied as a useful tool for characterization of metals mobilization from the particulate matter.

Microstructural and Mechanical Characteristics of Cladding Billets with Different Clad Ratios

AA4045/AA3003 cladding billets with different clad ratios were fabricated by direct chill casting process. The macrostructures, microstructures, compositions distribution and the mechanical properties near the bonding interface were investigated in detail. The results show that the cladding billet with few defects could be obtained by semi-continuous casting process. The metallurgical bonding was formed due to the diffusions of elements. The decreasing of clad ratio changed the microstructure at the interface and reduced the thickness of diffusion layer. The hardness around the interface is higher than that of AA3003 side but lower than that of the other side, indicating that the interface yield strength is also higher than that of AA3003. After extrusion process, the characteristics of the interface remain that of as-cast cladding billet.

Microstructure and Properties of Aluminum-Copper Composites Prepared by Hot-Pressure Sintering

Aluminum (Al) and Copper (Cu) have been used in graded density impactors. Al-Cu composites with different compositions have been prepared by hot pressing sintering. Intermetallic compounds were produced when the temperature was above 723 K, while they can’t be found at the temperature of 723 K. The relative density of Al-Cu composites from pure Al to pure Cu consolidated at 723K all exceeded 98.5%. The optimum sintering conditions were then determined to sintering temperature of 723 K, uniaxial pressure of 100 MPa, and duration time of 2 h. Al and Cu were mixed homogeneously and well compacted, and no obvious pores were found. The thickness of diffusion layer between Al and Cu was very thin, only about 0.6 μm. The wave impedance values increased almost linearly from 16.98×106to 40.66×106kg/m2·s with increasing Cu content in Al-Cu composite from 0 to 100 vol.%, which was well consistence with the values calculated according to the rule of mixtures. The elastic modulus of different compositions matched well with the theoretical model of Voigt and Reuss. Highly densified Al-Cu composites without intermetallic compounds were successfully prepared using hot-pressure sintering, which was the basis of fabricating Al-Cu system graded density impactors.

Study on Thermal Conductivity of Diffusion Layer of Coated Cutting Tools

Cutting temperature is the main factor to be considered in the select of coated cutting tools, so the study on the temperature of coated cutting tools is of practical significance. Diffusion layer of coated cutting tools has important implications on cutting heat generation and temperature distribution. In this paper, thickness of diffusion layer is determined by making use of spectrum analysis method to observe elements diffusion between coating and substrate of coated cutting tools. By dividing the diffusion layer into two parts on both sides of interface of coating and substrate, diffusion layer model is established. By integrated use of calculation method of Maxwll-Eucken model, Series model and equivalent thermal conductivity of multi-layer materials, thermal conductivity calculation formula of diffusion layer is derived. Method of thermal conductivity calculation when combining coating and diffusion layer into a whole layer is also put forward. Results of this paper have wide significance for experiment and simulation study on coated cutting tool temperature.

Effect of Diffusion Heat Treatment on Thickness of Cold-Rolled Cu/Al Composite Laminate Interface

The experiment has taken composite algorithm of cold rolling to prepare copper and aluminum composite laminate, studied the influence of diffusion heat treatment on the interface of copper and aluminum composite laminate. After Analyzed the relationship between the thickness of diffusion layer and diffusion heat treatment parameters, the experiments show that diffusion heat treatment temperature and diffusion time has influence on formation and size of the diffusion layer. At the same heat treatment temperature, the thickness of diffusion layer has parabolic relation with diffusion time with diffusion time extending and thickness of diffusion layer increasing. And the thickness of diffusion layer is increasing at the same heat treatment time. And the thickness of diffusion layer has exponential relation with diffusion heat treatment temperature. Quantitative analyzed the relationship between diffusion heat treatment parameters and diffusion layer thickness, and established a formula to describe the interface thickness and diffusion of heat treatment temperature and time.

Study on the Composite Interface of 4045/3004/4045 Aluminum Alloy Ingot

In this research, 4045/3004/4045 composite ingots were obtained by a semi-continuous casting process. The macrostructure, microstructure, elements distribution, mechanical properties of 4045/3004/4045 triple layers composite were studied. The results show that the composite interface is planar and clean with little evidence of porosity can be achieved by an optimum semi-continuous casting technology. The thickness of diffusion layer near composite interface can be controlled less than 30 μm. The bonding strength can reach to 100MPa which belongs to a kind of metallurgical bonding.

Microstructure and Properties of Interface High-Speed Steel Reinforced by In Situ VC /35CrMo Compound Roll

The high-speed steel (HSS) reinforced by in-situ VC /35CrMo compound roll was produced by electromagnetic semicontinuous casting. The element distribution and the structure morphology of the interface were analysed, and the mechanical properties were tested. The results indicate that the thickness of diffusion layer is around 50μm. The microstructure of the diffusion layer is pearlite, and next to the diffusion layer, the microstructures are ferrite and pearlite at the alloyed steel side. There are in-situ VC particles in martensitic matrix. At the high-speed steel side. The microhardness of HSS and 35CrMo is about 700HV and 250HV, respectively, and that of diffusion layer is near 350HV, which is between that of HSS and 35CrMo. The impact toughness is 100 Jcm-2. On the basis of the experiment, the interface of compound roll prepared by electromagnetic semicontinuous casting obtains good microscopic structure and mechanical properties, which are the results of the metallurgically bonded interface.