Yu. G. Gurevich

Effect of composition and porosity on the hardenability and hardness penetration of structural powder steels

ConclusionsThe effect of porosity (Θ > 10%) on the hardenability of the powder steels is stronger than the effect of carbon content. The role of these factors changes with the reduction of porosity (Θ < 10%) and the carbon content exerts a stronger effect on the hardenability of the steel. After hot pressing, the hardenability of the powder steels approaches the hard-enability of the dense steels of a similar chemical composition.The hardenability of the alloy powder steels at a constant carbon content and porosity is independent of the degree of alloying of the steel.The strength of the effect of complex alloying on the hardness penetration of the powder steels increases with decreasing porosity, especially after hot pressing and annealing as a result of the more efficient homogenizing of the structure with respect to carbon and alloying elements.

Thermodynamics of the chlorination of manganese oxide in the presence of iron

ConclusionsA diagram of the stable state of chloride phases in equilibrium with the [Fe-Mn]s solid solution has been constructed for the Fe-Mn-Cl-H-O system. It is shown that during chlorination at 1323–1423°C oxides are fully reduced. Chlorination is experienced almost exclusively by manganese, while iron passes into the solid solution. With the aid of the diagram it is possible to determine the composition of gaseous phases ensuring stability of gaseous manganese chlorides for any desired manganese concentration in iron.

Wear-resistant coatings of white cast iron on powder steels

A relatively simple process for coating of porous powder steel parts with a wear-resistant porousless layer of white cast iron has been developed. The wear resistance of the coating is comparable with that of high-chromium cast iron.

Transformation of supercooled austenite in sintered steels during continuous cooling

In the present work thermokinetic diagrams were constructed using data yielded by austenite transformation investigations carried out with a high-speed magnetometer fitted with a ferromagnetic probe [3, 4]. Magnetometric measurements were made on specimens with densities of 6.50, 7.00, and 7.78 g/cm 3, machined from impact test specimens produced by single pressing and sintering and also by hot forging. Transformations were studied in ZhGr0.5 and ZhGr0.5N2M sintered steels of the following chemical compositions (%):

Thermodynamics of the impregnation of iron alloys with chromium from a chloride phase

Conclusions1.A diagram of stable existence of chloride phases in equilibrium with a metallic solution has been constructed for the four-component Fe-Cr-Cl-H system.2.It is shown that in the chlorination of iron and chromium an equilibrium is set up in which either gaseous chlorides alone or both liquid and gaseous chlorides can coexist with a metallic Fe-Cr solution.3.Gaseous phase compositions have been determined ensuring the optimum values of parameters and the required degree of impregnation of iron with chromium from a chloride phase, as well as conditions necessary for the continuous impregnation of iron with chromium. It is shown that, to achieve this, provision must be made for the escape of gases from the container.4.Using calculated data, it is possible to determine the optimum conditions for the diffusion impregnation of iron alloys with chromium through a chloride phase.

Diffusion chromizing of grey cast iron by reaction with chromium oxide

The possibility is demonstrated by experiment for a simple chromizing method and subsequent surface hardening of objects made of ferritic-pearlitic grey cast iron with the aim of improving their wear resistance. The method provides an object surface layer hardness commensurate with laser hardening.

Development of technology for strengthening gray cast iron components by heating in contact with iron scale

Reaction of cast iron base with iron oxide FeO at 1173–1373 K is studied. It is shown that oxidation of cast iron base carbon promotes transformation of ferrite into austenite, and with rapid cooling this is converted into martensite. The hardness of ferritic-pearlitic cast iron after quenching is commensurate with that of malleable cast iron.

Manufacturing technology for white-iron smoothing tools used with nonferrous metals

Electrocontact chemical and thermal treatment of steel is developed. This process applies a white-iron layer at its surface, so as to increase the wear resistance. The structure and properties of the steel surface after treatment are investigated. It is found that, after the proposed electrocontact treatment, carbon-steel tools may be used to smooth the surface of nonferrous metals.

Heat treatment of lock rings made of SP100D3 steel crawlers of T-170 tractor by combining sintering with quenching

The modification of domestic tractors using a new moving part predetermined the aim of this work: examination of the kinetics of austenite transformation in continuous cooling of SP100D3 steel, develop the main parameters of the lock rings and the heat treatment conditions resulting in high service properties of the components. The SP100D3 steel (0.7-1.2% C, 2.7-3.0% Cu, balance-iron) was produced from PZh2M2 iron powder [1], PMS-1 copper powder [2], and GK-2 graphite powder [3]. Specimens with a density of 6700-6900 kg/m 3 were produced by onesided pressing in a closed pressing mold in a P6228 hydraulic press with a force of 700-900 MPa. To develop the optimum sintering and quenching conditions, the kinetics of transformation of austenite during continuous cooling were examined. Thermokinetic diagrams were constructed on the basis of the results of magnetometric investigations carried out on pressings 1 x 10 x 50 and 2 x 10 x 50 mm in size [4]. The optimum temperature of cooling after sintering and austenitizing prior to quenching was determined. After quenching at 1023, 1073, and 1123 K for 6.102 sec, the specimens were cooled in oil. Mean hardness values were 361,435, and 380 I/V, respectively. Lower hardness after quenching from 1023 and 1123 K was determined by the formation of ferrite (to 10%) and retained austenite (to 15%) in the martensitic structure. The optimum cooling temperature after sintering and austenitizing and prior to quenching was 1073 K. The cooling rate from the anstenitizing temperature was varied in the range from 2 to 300 deg/sec, using media with different cooling capacity. The variation of the cooling rate made impossible to achieve regular changes of the temperature and the extent of transformation of supercooled austenite. The results of examination of the development of transformations during continuous cooling were used to plot the thermokinetic diagrams and the diagram of the rates of breakdown of supercooled austenite of SP100D3 steel (Fig. 1). When SP100D3 steel is cooled from the austenitizing temperature at a rate of 300 deg/sec martensite forms in its structure. The temperature of the start of martensite formation (Ms) was 508 K. Regions of retained austenite were distributed between the martensite needles. The tetragonality of martensite was Cla = 1.025, its microhardness 7150 MPa. The decrease of the cooling rate from 160 deg/sec did not cause any changes in the structure and temperature M s, and the microhardness was 6710 MPa. Cooling at a rate of 140 deg/sec decreased the M s temperature to 515 K, and the amount retained austenite in the structure increased to 15%. The decrease of the cooling rate to 90 deg/sec resulted in pearlitic transformation in the range 805-627 K and increased the M s temperature to 519 K. The structure consisted of sorbite-like pearlite (1%), martensite (84%), and retained austenite (15%). With a further decrease of the cooling rate, the amount of pearlite in the structure of the quenched steel increased. For example, in cooling at rates of 85 and 75 deg/sec 6-8% of sorbite-like pearlite with a microhardness of 3960 MPa formed, and at 50 deg/sec the structure contained 70% of pearlite. The M s temperature was 537 K. In the cooling rate was decreased to 20 deg/sec, a small amount of ferrite appeared in the structure which increased with a further decrease of the cooling rate. For example, when the cooling rate was decreased from 10 to 2 deg/sec, the amount of ferrite increased to 7%. The special feature of the Structure after cooling at a lower rate is the large scatter of the dispersion of pearlite. The effect of the cooling rate of the SPI00D3 steel with a porosity of 15 % on the kinetic parameters of austenite transformation and the hardness of the structural components is reflected in Table 1. The thermokinetic diagram of the SP100D3 steel contains 3 regions of transformation: ferritic, pearlitic, and martensitic. Bainitic transformation is not found on the diagram. In the temperature range 673-423 K the rate of transformation

Thermodynamic analysis of siliconizing of steel articles via a chloride phase

Thermodynamic analysis of the Fe-Si-Cl-H system shows that iron siliconizing via a chloride phase is technologically feasible. Silicon is more easily chlorinated at a temperature below 1000 K, and silicon transport via the gas phase is more likely. The results obtained may be used to develop production processes for siliconizing iron surfaces of articles.