Investigation of the Processes in Torches for High‐Speed Gas‐Plasma Spraying of Powder Materials with the Use of the Flow‐Rate Method of Action on the Flow

The comparative characteristic of torches with geometric and flowrate methods of control of the characteristics of a twophase flow are given. Based on the mathematical model proposed, the advantage of the flowrate method is shown by calculation. By using particular examples, the estimates of the optimum values are given for the relation of the flow rates in feeding units and for the length of the heating portion for torches with a flowrate method of control of the twophase flow.     

Influence of Turbulence on the Deposition of Particles from a Gas‐Dispersed Flow on the Wall

Simulation of the scattering and deposition of dispersedphase particles in the region of interaction of a turbulent flow with an obstacle is considered. The regimes and distinctive features of deposition of particles in the vicinity of a critical point are investigated under different conditions. The sedimentation coefficient of the impurity is calculated as a function of the parameters of unperturbed flow and the particle size. The results of the calculations are compared to the data obtained without allowance for the influence of the fluctuations of the carrierflow velocity on the motion of the impurity.     

Heat Exchange on the Front Surface of a Blunt Body in a High‐Speed Flow Containing Low‐Inertia Particles

The method and results of an experimental investigation of the heat exchange on the front surface of a sphere in a supersonic flow containing particles of diameter d = 0.12–2.4 m and hollow particles of d = 160 m are presented. It has been revealed that in the case where even very small particles of d = 0.15 m are contained in an undisturbed flow and their concentration is low (of the order of a percent), the heat flux in the region of the critical point of the model markedly increases. A comparison of the experimental data with the data of calculations of the heat exchange in the region of the forward critical point which are based on the theory of a twophase laminar boundary layer has been made. A glow near the surface of the model was observed in the experiments conducted in total darkness.     

Process of Cooling of a High‐Temperature Two‐Phase Flow

A technique and a design of a transducer for measuring the enthalpy of twophase flows using the thinwall method have been developed. Working formulas for calculating the heat capacity and the enthalpy of a gas flow are substantiated. Results of a test of the transducer in hightemperature flows of powder gases, including those after the packing of a coolant, are presented. The results obtained show that cooling of powder gases due to an endothermic reaction makes it possible to decrease the enthalpy flux by a factor of 5 and the temperature by a factor of 2.     

Hot Deformation and Modeling of Flow Stress for a Ti-containing HSLA Steel

Single-stage and double-stage interrupted hot compression tests for simulating hot rolling have been carried out for a Ti-containing HSLA steel (10Ti). Physical simulation of hot rolling was in progress utilizing a Thermecmastor-Z simulator in 850~1150℃ and strain rate of 0.1~60 s-1.A model for residual strain ratio λ was designed, and a model of flow stress considering residual strain has been obtained. The hot deformation behaviour at various strain rates has been studied.     

Thermophysical Properties of a Chromium–Nickel–Molybdenum Steel in the Solid and Liquid Phases

Numerical simulation of vacuum arc re-melting, pressurized or protective electro-slag re-melting, and ingot casting have become quite important in the metal industry. However, a major drawback of these simulation techniques is the lack of accurate thermophysical properties for temperatures above 1,500 K. Heat capacity, heat of fusion, density, and thermal conductivity are important input parameters for the heat transfer equation. Since, direct measurements of thermal conductivity of alloys in the liquid state are almost impossible, its estimation from electrical conductivity using the Wiedemann–Franz law is very useful. The afore-mentioned thermophysical properties of several steels are investigated within the context of an ongoing project. Here, we present a full set of thermophysical data for the chromium–nickel–molybdenum steel meeting the standard DIN 1.4435 (X2CrNiMo18-14-3); these values will be used by our partner to simulate various re-melting and solidification processes. Wire-shaped samples of the steel are resistively volume-heated, as part of a fast capacitor discharge circuit. Time-resolved measurements with sub-μs resolution of current through the specimen are performed with a Pearson probe. The voltage drop across the specimen is measured with knife-edge contacts and ohmic voltage dividers, the temperature of the sample with a pyrometer, and the volumetric expansion of the wire with a fast acting CCD camera. These measurements enable the heat of fusion, the heat capacity, and the electrical resistivity to be determined as a function of temperature in the solid and liquid phases. The thermal conductivity and thermal diffusivity are estimated via the Wiedemann–Franz law.     

Influence of Flow Angularities in a Hypersonic Ramjet Diffuser on the Formation of the Shock‐Wave Structure of the Real Gas Flow

We have investigated the shockwave structures arising at the entrance to the engine section of hypersonic aircraft and the influence on the process of their formation of the flow angularity after oblique shock fronts incident inside the diffuser with a different type of interaction (Mach or regular). To take into account the real properties of the atmosphere, we used the effective adiabatic exponent method permitting determination of the topology of shockwave patterns and calculation of the gas and thermodynamic parameters in various flow zones between the shock fronts in a wide range of diagnostic variables for the Earth's atmosphere.     

Quantitative Mossbauer Study on Retained Austenite and Carbide in High Speed Steel

The retained austenite in high speed steel oftwo different heat treatment regimes wasquantitatively,determined by transmissionMssbauer spectroscopy (TMS),backscatteringX-ray geometry,Mossbauer spectroscopy (BXMS)and X-ray diffraction technique.The results meas-ured by these methods were in agreement with eachother.It was demonstrated that the concentrationof carbides in high speed steel could be measured bytransmission Mossbauer spectroscopy or Mossbau-er spectroscopy in backscattering X-ray geometryaccurately.     

The Optimum Thickness of a Cooled Coated Wall Exposed to Local Pulse‐Periodic Heating

In the present work, the optimum thickness of a plane wall with a heatshielding coating that ensures the minimum steadystate temperature of the most heated point of the wall is determined. On the unprotected side the wall is cooled by a medium whose temperature and heattransfer coefficient are constant, whereas on the side of the coating the wall is exposed to a heat flux with an intensity of the Gaussian type in the pulseperiodic regime.     

Method of Protection and Diagnostics of the Combustion Chamber Wall on Exposure to a High‐Intensity Heat Flux

In the present work, consideration is given to the method of thermal protection of the walls of highpower installations (plasmatrons and gasphase nuclear reactors), made of porous refractory materials, with the use of gasdust protection. The algorithm for determining the mechanical, thermal, and thermophysical characteristics of the porous wall of a combustion chamber from the measured increase in the pressure on the exterior surface of the wall is given.     

Study on Laser Transformation Hardening of HT250 by High Speed Axis Flow CO2 Laser

In this article, laser transformation hardening of HT250 material by high speed axis flow CO2 laser was investigated for first time in China. Appropriate laser hardening parameters, such as laser energy power P(W), laser scanning rate V(m/min), were optimized through a number of experiments. The effect of the mentioned parameters on the hardened zone, including its case depth, microhardness distributions etc., were analyzed. Through the factual experiments, it is proved that axial flow CO2 laser, which commonly outputs low mode laser beam, can also treat materials as long as the treating parameters used are rational. During the experiments, the surface qualities of some specimens treated by some parameters were found to be enhanced, which does not coincide with the former results. Furthermore in the article, the abnormal phenomenon observed in the experiments is discussed. According to the experimental results, the relationship between laser power density q and scanning rate V is shown in a curve and the corresponding formulation, which have been proved to be valuable for choosing the parameters of laser transformation hardening by axial flow CO2 lasers, was also given.     

Effect of Hot Deformation on Pearlite Transformation of 86CrMoV7 Steel

The continuous cooling transformation (CCT) diagrams of 86CrMoV7 steel samples including hot deformed and not hot deformed were constructed by dilatometry, metallography and transmission electron microscopy (TEM). The results showed that hot deformation accelerated pearlite transformation and fine pearlite microstructure. Moreover, the undissolved carbides became the nucleating sites of pearlite, accelerated pearlite formation and fine pearlite if the steel had been deformed at high temperature. In contrast, undissolved carbides did not make any influence on pearlite transformation if the steel had not been deformed at high temperature.     

Parameters of a Gas‐Powder Flow Formed by a Cumulative Accelerator and Realizing the Effect of Superdeep Penetration

The development of a gaspowder flow formed by an explosive accelerator with a cumulative recess in its lower part is numerically investigated. A comparative analysis of two variants of a cumulative system of impelling that are basic to the effect of superdeep penetration has been carried out, and their integral parameters have been estimated.     

Heat and Mass Transfer in a Two‐Component Developed Turbulent Gas‐Vapor‐Droplet Flow

A calculation model is developed and a numerical study is made of the heat and mass transfer characteristics in a turbulent gas–vapor–droplet flow moving in a round tube. The model takes into account the evaporation of droplets, the diffusion of vapor into air, and the acceleration of a carrier flow. Distributions of the parameters of the twophase flow are obtained with respect to the tube radius for different initial concentrations of the gas phase. Heat and masstransfer calculations are compared to the experimental and numerical works. On the whole, the evaporation of the droplets in the vaporgas flow leads to the intensification of heat transfer as compared to a onecomponent vapordroplet flow and singlephase flow of vapor.     

Penetration of the Material of Particles from a High‐Velocity Flux in Collision with a Steel Obstacle to Large Depths

Experimental data on the punching of steel obstacles of thickness 20 mm are given, which show that, in collision and penetration, the particle and obstacle materials go out onto the rear side of the obstacle in the form of thin jets and their interaction with the package of electronic elements is responsible for the degradation of these elements located behind the obstacle.     

High Manganese Steel Alloying Process and Its Influence on Microstructure and Properties of the Steel

The influence of two kinds of alloying processes, adding Nb (or Ti) and N-Mn alloy as well as adding Nb (or Ti) and spraying N2, on microstructures and properties of a high manganese steel has been studied. It has been found that adding Nb(or Ti), accompanying with N-Mn alloy, is unfavourable to microstructure compactness of the high manganese steel, but adding Nb (or Ti)and spraying N2 into the melt is good for refining austenitic grain, forming a lot of hard particles and improving microstructure compactness. The mechanical properties of the high manganese steel have relation to the content of elements Nb or Ti. Its fracture mode will turn ductile fracture into brittle cleavage fracture gradually. By X-ray and TEM analysis, it is proved that the austenite can be transformed to deformation-induced α martensite after adding a certain amount of element Nb (or Ti). The microstructure transformation of alloying high manganese steels through deformation is one of methods for strengthening austenite matrix and increasing the work-hardening rate as well as improving antiwear property.     

Enhancement of a Magnetic Field in a Perfectly Conducting Medium on Penetration of a High‐Velocity Jet into It

We consider the possibility of enhancement of a magnetic field created in a conducting medium on penetration into it of a highvelocity striker moving across the magneticinduction lines. For the case of a perfectly conducting target, an estimate is obtained for the rate of increase of the field intensity in the region of contact with the head part of the striker. A dimensionless parameter is introduced that characterizes the relationship between the rates of generation and diffusion of the field on penetration into a material of finite conductivity. Based on a model that takes into account the force action of a compressed field, the special features of the flow that arises on penetration of a highvelocity cumulative jet into a perfectly conducting target with a transverse magnetic field are analyzed.     

High-Temperature Interaction of 08Cr18Ni10Ti Chromium–Nickel Steel with Model Borosilicate Waste Form Materials

Inorganic Materials - Using electron microscopy and electron probe X-ray fluorescence microanalysis, we have studied chemical and structural changes in the zone of high-temperature contact between...     

Revealing Precipitate Development During Hot Rolling and Cooling of a Ti–Nb Micro-Alloyed High Strength Low-Alloy Steel through X-Ray Scattering

High-energy synchrotron X-ray small-angle scattering (SAXS) is used to study the precipitate development during hot rolling and cooling of a commercial Ti–Nb micro-alloyed, high-strength, low-alloy (HSLA) steel. To study precipitation during hot rolling conditions, Gleeble and dilatometer trials are made. Samples are then studied at room temperature using SAXS in conjunction with transmission electron microscopy (TEM). TEM is used to determine the morphology and composition of the precipitates, whilst both TEM and SAXS are used to study the particle sizes. One major advantage with high-energy SAXS is the ability to make measurements after a minimum of sample preparation and in transmission geometry, as opposed to just at prepared surfaces, plus the possibility to determine volume fractions of the precipitates. The measurements show that after deformation at high temperature, particle coarsening occurs and the volume fraction of precipitates increases after holding for 20 s at 900 °C which confirms strain-induced precipitation at finishing rolling conditions. The measurements show that holding at 600 or 650 °C for one hour gives a larger volume fraction of nanosized particles. Coiling simulations with slow cooling from 600 to 470 °C show coarsening of particles and an increase in the volume fraction of the smaller particles compared to holding at a constant temperature.