Mechanical properties and fracture upon static tension of the high-carbon steel with different types of pearlite structure

The hardness and mechanical properties of the U10 steel (1.03 wt % C) with pearlite structures that were formed by isothermal decomposition at temperatures of 650°C (coarse-lamellar pearlite) and 500°C (fine-lamellar pearlite) as well as upon subsequent annealing of fine-lamellar pearlite at a temperature of 650°C for 10–300 min have been studied upon tensile tests. Fractures of the steel with different types of pearlite structure have been examined using scanning electron microscopy. The interrelation between the mechanical properties and the structural features and character of fracture has been analyzed for this steel with pearlite structures differing in the dispersity, morphology, and defect structure of cementite, and in the levels of solid-solution strengthening and microdistortions of the ferrite-constituent lattice.     

Enhancement of bending strength of heat-resistant steel by ion carbonitriding

The heat-resistant steel 20Kh3MVF-Sh is used for toothed gears employed in pumps of turbojet engines. In service, the working surface of the gears is subjected to intensive wear. Using gas-phase carburizing to case-harden such gears has proven to be insufficiently effective. In this work we have investigated the structure, the chemical composition, and the wear resistance of 20Kh3MVF-Sh steel after ion carbonitriding. We have obtained regression equations relating the wear resistance characteristics to the carbon and nitrogen concentration and the hardness of the diffusion layer. We have developed a combination process for ion carbonitriding which increases the wear resistance or steel 20Kh3MVF-Sh.N. É. Bauman State Technical University, Moscow. MAKB TEMP. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 9–13, June, 1994.     

Processing ceramic-matrix composites using electrophoretic deposition

A novel, cost-effective processing technique for manufacturing ceramic-matrix composites (CMCs) containing two-dimensional woven-fiber reinforcement has been developed. The technique relies on the electrophoretic deposition (EPD) of ceramic sols on/into the fiber preforms to achieve the required impregnation. The laboratory-scale results achieved thus far indicate that the processing approach offers great potential for the manufacture of high-quality, composite products with dual-component oxide matrices for high-temperature structural applications.     

Spin Extrusion - A New Partial Forming Technology based on 7 NC-Axes Machining

Hollow shape component approaches, applied to shafts and similar workpieces, represent a major potential for ground-breaking innovations in lightweight engineering and safety designs. Among suitable forming technologies, spin extrusion is a pioneering and particularly flexible hollow-shaping technique. All outside form elements, straight or stepped cylinders, cones or spherical rotation elements emerge just from the kinematics of tools. The inside hollow shapes, as e.g. circular cross-sections, shaft to collar connections such as spherical triangles, polygons, splines or dovetail forms are manufactured with a shaping mandrel. Spin extrusion can be applied first and foremost at dimensions that are unattainable with other techniques. The application includes hollow shafts, thick-walled cups and semi-finished tubular products that are not to be found in off-the-shelf cross-sections. In these cases the possibility for using of massive bars is connected with very high price advantages. Furthermore material-saving machining is attracting special attention for high-grade materials.The paper characterizes substantial steps of process analysis and the appliance of a new, derived from the bound method, numerical simulation method for spin extrusion process. Holistic process analysis is the prime factor for process capability. The specific application of the developed special methods of simulation, the accumulation of process data and the integrating into the Computer numerical control of spin extrusion machine is a precondition guaranteeing high-quality assurance.     

The treatment influence on the electric strength and conductivity of fibroin

The influence of thermal treatment and liquid nitrogen treatment of cocoons on the electric properties of natural silk fibroin has been studied. It is found that, at the cocoon treatment by liquid nitrogen, the ratio of the amorphous and crystalline parts of the fibroin is preserved and the concentration of submicrocracks in them changes to a lesser extent than at treatment by heated air and a UHF field. The increase of the degree of crystallinity in the polymers leads to a certain increase of their breakdown voltage.     

Oxidation Behavior of Rh–30Ni–18Nb Refractory Superalloy

The isothermal-oxidation behavior of Rh–30Ni–18Nb refractory alloy was investigated up to a period of 312 hours in air from 1000 to 1350°C. A comparison of the oxidation behavior of this alloy with a conventional Ni-base superalloy (Inconel 713 C) shows an order-of-magnitude higher oxidation resistance. This experimental alloy oxidizes by forming alternate layers of Nb₂O₅ and RhO while NiO is on the surface in contact with air. Optical and scanning-electron microscopy (SEM) was used to study the microstructure and morphology for the characterization of the oxides. Thermal stability of the alloy for extended periods of exposure to air at 1400°C was studied using transmission-electron microscopy (TEM).     

Developments in Plasma Processes for Extractive Metallurgy

With the recent availability of commercial plasma-generating devices capable of reliable performance at powers as high as 30 MW, the applications of plasma technology in high-temperature extractive metallurgy are rapidly increasing. Some of the more promising process developments are reviewed in this paper, as are newer reactor designs.     

TBC experience in land- based gas turbines

This paper summarizes prior and on-going machine evaluations of thermal barrier coatings (TBC) for power generation, that is large industrial gas turbine applications. Rainbow testing of TBCs on turbine nozzles, shrouds, and buckets are described along with a test of combustor liners. General Electric Power Generation has conducted more than IS machine tests on TBC turbine nozzles with various coatings. TBC performance has been quite good, and additional testing, including TBCs on shrouds and buckets, is continuing. Included is a brief comparison of TBC requirements for power generation and aircraft turbines.     

A Finite Element Simulation of the Electroplating Process

This paper describes the development, comparison and validation of both 2-D and 3-D models of the electroplating process in which the current density distribution, generated using the Finite Element Method (FEM), is used together with Faraday's law of electrolysis to determine the local plating depth. Prior to work on industrial components, a preliminary investigation was undertaken on the electroplating of a square copper cathode (work piece) with a parallel lead anode of identical shape. The results described here show good agreement, particularly in 3-D and are considered to validate the model sufficiently for it to be used for electroplating tooling design.