RU2447175C1 - Modifying agent for nickel alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed composition contains the following substances, in wt %: titanium carbonitride - 2.5, titanium - 19-21, chromium - 1.4 - 1.6, molybdenum - 9-11, tungsten - 9-11, niobium - 9-11, aluminium - 32-38, nickel - 9-11, manganese - 0.9-1.1. Particle size of fine titanium carbonitride powder makes 0.01-0.05 mcm, that of titanium makes 0.01-0.1 mcm, while that of chromium, molybdenum, tungsten, niobium and aluminium makes 4-50 mcm, and particle size of nickel and manganese does not exceed 20-30 mcm.

EFFECT: alloy with fine-grained uniform structure and high physical properties.

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Description

The invention relates to the field of metallurgy, and in particular to the modification of heat-resistant alloys based on nickel like ZhS with ultrafine powders of refractory compounds.

The prior art modifier for nickel alloys containing 0.5-1.5 wt.% Nitrogen, 1.7-6.8 wt.% Titanium, 30-50 wt.% Chromium, 0.1-1.0 wt. .% boron, the rest is nickel. The modifier contributes to the refinement of the structure and hardening of the alloy with titanium nitride particles (AS USSR 384918, Institute of Casting Problems of the Ukrainian SSR, 01.10.1973).

As the closest analogue, a modifier was chosen to improve the properties of castings from heat-resistant alloys containing 20-25 wt.% Molybdenum, 60-70 wt.% Chromium, nickel - the rest (RF patent 2337167 C2, 10.27.2008).

A disadvantage of the known modifiers is that the modification of refractory metals and particles of refractory compounds formed in the form of a ligature or introduced in the form of a powder with a particle size greater than a micrometer does not ensure their uniform distribution over the melt volume.

The problem to be solved as a result of the implementation of the claimed invention is to select the optimal chemical and physical composition of the modifier, which provides an effective effect on the micro- and macrostructure.

The technical result of the invention is to obtain an alloy with fine grain uniformly distributed throughout the volume, and providing high stable physical and mechanical properties.

The specified technical result is achieved due to the fact that an ultrafine titanium carbonitride powder, titanium, tungsten, niobium, aluminum and manganese powders are additionally introduced into the known modifier containing molybdenum, chromium and nickel in the following ratio, wt.%:

titanium carbonitride 2.5 titanium 19-21 chromium 1.4-1.6 molybdenum 9-11 tungsten 9-11 niobium 9-11 aluminum 32-38 nickel 9-11 manganese 0.9-1.1

while the particle size of the ultrafine titanium carbonitride powder is 0.01-0.05 microns, the particle size of titanium powder is 0.01-0.1 microns, and the particle size of the chromium, molybdenum, tungsten, niobium and aluminum powders is 4-50 microns and the particle size of nickel and manganese does not exceed 20-30 microns.

The titanium content exceeds the content of titanium carbonitride by approximately 10 times, since this is necessary to create a cladding layer of titanium on the particles of carbonitride. Moreover, when the titanium content is less than 19 wt.%, The full cladding of carbonitride grains is not provided, and when the titanium content is more than 21 wt.%, The temperature of the products of the exothermic reaction with nickel decreases.

The aluminum content of 32 to 38 wt.% Was chosen to ensure the passage of stable SHS processes, as a result of which the modifier particles, under the influence of thermal energy of the metallothermic reaction released during the combustion of aluminum inside the briquette, will “break” the briquette from the inside and spread titanium carbonitride particles throughout the volume serving as crystallization germs. When the aluminum content is below 32 wt.% In the modifier, sufficient force will not be created to disperse the particles over the melt volume; at a content exceeding 38 wt.%, The melt is oversaturated with aluminum, which negatively affects the properties of the alloy.

When the content of chromium, molybdenum, tungsten, niobium is below the minimum values, the grain size of nickel increases, in the case of contents of these components above the maximum values, the exothermic reaction along the modifier briquette is interrupted and the specified alloy composition is not ensured.

The nickel content is selected from the condition that the modifier forms a matrix based on MeC with a nickel content of about 3%.

The particle size of titanium carbonitride below 0.01 μm promotes particle aggregation, an increase in the growth time of the modified phase and reduces the uniformity of the distribution of crystallization centers, above 0.05 μm it reduces the uniformity of the modified metal.

The particle size of titanium is 0.01-0.1 μm due to the fact that when particles are below 0.01 μm, particles are aggregated, and when the particle size is above 0.1 μm, titanium carbonitride particles are non-uniformly clad.

The particle size of chromium, molybdenum, tungsten, niobium and aluminum below 4 microns leads to aggregation of particles, and above 50 microns the propagation of the exothermic reaction along the modifier briquette is interrupted.

The particle size of manganese and nickel does not directly affect the technical result and can be no more than 20-30 microns.

The introduction of a modifier in a wide range of temperature-time parameters of the melting affects the nature of the precipitation of carbide inclusions in the metal, among which the most common is MeC carbide, which has a skeletal or line morphology in nickel alloys. The use of complex modification technology leads to a decrease in size and a change in the dendritic cell, which is caused by an increase in the crystallization rate of the modified alloy in the first stage of crystallization. In addition, the morphology and topography of the carbide phase changes - from precipitates of the type of films arranged in a chain and having the form of a “Chinese character” that form a frame along grain boundaries to compact rounded inclusions. In addition, after modification, dendritic segregation is significantly reduced, and the elements are redistributed more evenly, ensuring equalization of the composition between the axes of the dendrites and the interaxal sections.

The ability to achieve the specified technical result is confirmed by the following example.

Example.

The powders of modifier components with specified particle sizes are mixed in the following ratio, wt.%: 2.5 titanium carbonitride, 20 titanium, 1.5 chromium, 10 molybdenum, 10 tungsten, 10 niobium, 35 aluminum, 10 nickel, 1 manganese. A briquette is formed from the resulting mixture by pressing at 20-50 MPa and sintering at a temperature of 850-900 ° C in vacuum for 30 minutes.

The nickel alloy obtained using such a modifier has a uniform dendritic structure with a grain size of 0.5-1.5 mm and containing globular carbides with a size of 4-8 microns.

Table 1 Physico-mechanical properties of the alloy ZhS6-U Object of study Temporary tear resistance, σ _in , MPa Carbide form The average grain size, mm Prototype alloy 855 globular 3-5 TiCN Modified Alloy 1100 globular 0.5-1.5

Thus, the use of a modifier containing titanium-clad ultrafine particles of titanium carbonitride allows one to efficiently and purposefully affect the micro- and macrostructure of the nickel alloy and to obtain fine equiaxed grain throughout the casting volume, providing high physicomechanical properties of the casting.

Claims (1)

Modifier for nickel alloys containing molybdenum, chromium and nickel powders, characterized in that it additionally contains ultrafine titanium carbonitride powder, titanium, tungsten, niobium, aluminum and manganese powders in the following ratio, wt.%:
titanium carbonitride 2,5 titanium 19-21 chromium 1.4-1.6 molybdenum 9-11 tungsten 9-11 niobium 9-11 aluminum 32-38 nickel 9-11 manganese 0.9-1.1,
while the particle size of the ultrafine titanium carbonitride powder is 0.01-0.05 microns, the particle size of titanium powder is 0.01-0.1 microns, and the particle size of the chromium, molybdenum, tungsten, niobium and aluminum powders is 4-50 microns and the particle size of nickel and manganese does not exceed 20-30 microns.