Properties Of Heat-resistant Alloys Research Articles

Modelling the composition of carbides in nickel-based superalloys of directional crystallization

Purpose: The specifics of the influence of alloying elements on the chemical composition of various types of carbides, their topology and morphology for a multicomponent system of the type Ni-5Cr-9Co-6Al-1Ti-11.7W-1.1Mo-1.6Nb-0.15C using the calculation method CALPHAD. It is shown that the obtained dependences closely correlate with thermodynamic processes occurring in the system. Design/methodology/approach: This work presents the results of studies of the distribution of chemical elements in the composition of carbides, depending on their content in the system. Findings: It was found that the influence of alloying elements on the composition of carbides is complex and is described by complex. Research limitations/implications: An essential problem is the prediction of the structure and properties of heat-resistant alloys without or with a minimum number of experiments. Practical implications: The obtained dependences can be used both for designing new heat-resistant alloys and for improving the compositions of industrial alloys. Originality/value: The value of this work is that the obtained dependences of the influence of alloying elements on the dissolution (precipitation) temperatures and the distribution of elements in carbides in the alloy of the Ni-5Cr-9Co-6Al-1Ti-11.7W-1.1Mo-1.6Nb-0.15C.

Comparative Study of the Structural-Phase State and Mechanical Properties of Ni–Cr(X) and Fe–Cr(X) Heat-Resistant Alloys Fabricated by Additive Technologies

Comparative studies of peculiarities of the formation, thermal stability of the structure, and mechanical properties of heat-resistant alloys based on iron and nickel and fabricated using additive technologies (ATs) by laser metal deposition and selective laser melting are performed. It is established that a cellular structure is formed in alloys fabricated by the laser metal deposition and small pores up to 200 nm in size are present. The structure of alloys fabricated by selective laser melting contains elements with a globular and lamellar morphology and incompletely melted regions, as well as large pores on the order of 5 μm in size. The possibility of manifestation of the nanophase hardening effect due to the presence of nanodimensional particles of chromium silicides is shown. A comparative analysis of mechanical properties of materials under study is performed. It is shown that iron-based alloys possess higher strength and lower ductility when compared with nickel alloys. All studied samples fabricated by selective laser melting have higher strength characteristics when compared with alloys fabricated by laser metal deposition. Short-term annealing at 900–1000°C for 1 h noticeably decreases both strength and plasticity in tensile and compression tests at room and elevated temperatures. Alloys based on iron and nickel fabricated by laser metal deposition and subjected to compression tests at t = 900°C have similar strength characteristics. In contrast with iron-based alloys, additional annealing of the nickel-based AT alloy almost does not decrease its strength characteristics.

Remelting effect on the properties of heat-resistant alloy in liquid state

Remelting effect on the properties of heat-resistant alloy in liquid state

Behavior of heat-resistant alloys and titanium alloys on cutting

The properties of heat-resistant alloys used for the manufacture of compressor blades are analyzed. The optimal cutting speeds for titanium alloys and heat-resistant alloys are determined. The dependence of the plastic strain and chip formation on the cutting speed in the broaching of such alloys is established.

An investigation into crystalline phases and nano structural and mechanical properties of HH heat resistant stainless steels

In the present work, the effects of different casting parameters including pouring temperature and cooling rate on stainless steel structures and mechanical properties of heat resistant alloy (HH) were studied. Mo nanoparticles were synthesized through sol-gel method and were coated on the stainless steel device using spin-coating method. The effect of coating layer on the device was studied by using XRD (X-Ray Diffraction) and FT-IR (Fourier Transform Infra red ) and SEM (Scanning Electron Microscopy) techniques. The obtained results indicated an enhancement of corrosion, surface abrasion protection without changing metal surface structure, and a reduction of leakage current through the stainless steel device. Furthermore, pouring temperature and cooling rate increase caused a fine grain structure to be acquired with less carbides and better distribution in the austenitic matrix.

Antifriction properties of heat-resistant alloys in hydrogen

We investigate the influence of hydrogen on friction properties of heat-resistant KhN55MBYu alloy and establish the main regularities of variation in the sliding friction coefficient in the process of operation of a shaft-bush couple depending on the temperature and pressure of hydrogen as well as on the rate and type of loading. Some recommendations concerning the efficient use of certain plasma and self-lubricating coatings for the operation of valve hydrogen engines are given.

Mechanical Properties of Heat-Resistant Alloys Exposed to Air and HTGR Helium at High Temperatures

The effect of a corroded surface layer on the tensile properties and the high-temperature low-cycle fatigue life was studied on Hastelloy-X and on Incoloy alloys 800 and 800H by comparing the properties between specimens exposed to air and high-temperature gas-cooled reactor helium at 1000/sup 0/C prior to testing and specimens aged under the same temperature/time conditions as those of exposed specimens. The ratio of the corroded surface layer to the total cross-sectional area was controlled at 1000/sup 0/C by environment, exposure time, and shape/size combinations of specimens. Tensile strength could be quantitatively expressed in terms of the intergranular oxidation, irrespective of the variation of materials and corrosive conditions. By comparing the low-cycle fatigue lives at 1000/sup 0/C between exposed and aged materials, it was clarified that lifetime was remarkably reduced by the formation of a corroded surface layer. However, fatigue life of aged material was less than that of solution-treated materials. These two opposing effects of corrosion and aging brought about a small difference in fatigue life between solution-treated and exposed materials.

Effect of protective coatings on the mechanical properties of heat-resistant alloys

Effect of protective coatings on the mechanical properties of heat-resistant alloys

原子力製鉄用耐熱合金のヘリウム及び還元ガス雰囲気中クリープ破断特性とその劣化

Creep rupture properties of heat resistant alloys with carbide or carbide and γ' precipitates were investigated in the temperature range from 900° to 1 050°C in He and reducing gas atmospheres. The degradation of the rupture strengths took place in the alloys, which have carbide as a strengthener, due to decarburization in He atmoshere at higher temperature than 1 000°C. In the alloy which was strengthened mainly by γ', the solutioning of γ' led to the degradation of the rupture strengths, but to the restoration of rupture ductilities in greater extent. A new method to predict the rupture life, steady state creep rate, etc. from 0.2% proof stress was proposed. In most cases, the method was found to be satisfactory in the sense that it represents the degradation behaviour of the alloys according to various causes.

Effect of prior action of temperature and force on the mechanical properties of heat-resistant alloy ÉI698VD

Effect of prior action of temperature and force on the mechanical properties of heat-resistant alloy ÉI698VD

二種類の高温ガス炉用不純ヘリウム中におけるNi基耐熱合金のクリープ破断特性

In order to investigate the effect of impure helium environments of HTGR (high temperature gas-cooled reactor) on the creep rupture properties of heat resistant alloys for intermediate heat exchanger tubes, a creep rupture test has been carried out on four nickel-base superalloys in two impure helium gases, He-2 and PNP-He, at 1000°C.All the alloys were decarburized in some extent in PNP-He, while some of them were carburized in He-2 during the creep rupture testing, indicating that carbon potential of the gases was lower in PNP-He than in He-2 at 1000°C.The alloy hardened by γ' (Ni3(Al, Ti)) precipitation, R4286, was suffered from the environmental effects resulting in the formations of γ' depleted zone, Al internal oxides and grain boundary carbide depleted zone beneath the alloy surface. The creep rupture life of this alloy in PNP-He was found to be one-third of that in He-2, which was mainly caused by the formation of carbide depleted zone along grain boundaries due to decarburization in PNP-He.The alloy hardened by α-W precipitation, KSN and 113MA, was suffered from the environmental effects resulting in the formations of α-W and grain boundary carbide depleted zones. The creep rupture life of KSN containing highest concentration of tungsten, 26%W, were found to be almost the same in the two environments, although this alloy was remarkably decarburized in PNP-He. Because KSN was mainly hardened by very fine precipitates of α-W, it was considered that the creep rupture life was little affected by decarburization.The alloy SZ was hardly decarburized in PNP-He, showing a good resistance to corrosion.

Effect of method of producing blanks on the mechanical properties of heat-resistant alloys

Effect of method of producing blanks on the mechanical properties of heat-resistant alloys