RU2237741C1 - Casting nickel-based alloy - Google Patents

Abstract

FIELD: metallurgy, in particular nickel-based alloy for build up of pats operating in severe condition of high temperature sulfide-oxygen corrosion.

SUBSTANCE: Claimed alloy contains (mass.%) carbon not more than 0.10, chromium not more than 32.0-35.0, tungsten 4.3-5.50, molybdenum 2.3-3.3, titan 0.50-1.10, aluminum 0.5-1.10, iron not more than 4.0, niobium 0.50-1.10, boron 0.30-0.55, cerium not more than 0.030, manganese not more than 0.50, silicium not more than 0.40, sulfur not more than 0.01, phosphorus not more than 0.05, additionally yttrium 0.03-0.05, and balance nickel. Present alloy exhibits improved processing strength when build up and maintained hardness and sulfide corrosion resistance when operating at high temperature.

EFFECT: nickel-based alloy with improved processing strength, hardness and sulfide corrosion resistance.

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Description

The invention relates to metallurgy, in particular to nickel-based alloys used for surfacing on parts operating in harsh conditions under high temperature sulfide-oxide corrosion.

Known casting heat-resistant alloy based on Nickel, containing the following components, wt.%: Carbon 0.06-0.12, chromium 15.0-16.7, cobalt 10.0-11.5, molybdenum 1.5-2, 5, tungsten 4.5-6.0, aluminum 2.4-3.2, titanium 4.2-5.0, yttrium 0.05, boron 0.02, zirconium 0.05, niobium 0.1-0 , 3, sulfur 0.008, phosphorus 0.008, manganese 0.30, silicon 0.30, iron 0.5, copper 0.07, nitrogen 0.01, bismuth 0.00005, lead 0.001, antimony 0.0005, arsenic 0, 0005. (Heat-resistant nickel alloy KhN58KVTYUMBL-VI (ChS70U-VI), TU 14-1-3658-83). The turbine blades of gas turbine units (GTU) are cast from this alloy, which have high operational properties: resistance to sulfide corrosion and thermal resistance to oxidation at high temperatures. During the repair of gas turbines, the worn surfaces of the blades are restored using surfacing.

It is ineffective to use the ChS 70U-VI alloy as an additive in reducing surfacing due to the low resistance of welded joints to the formation of hot cracks, i.e. during argon-arc welding, the alloy has a low technological strength.

The closest in technical essence is a casting heat-resistant alloy based on nickel, containing the following components, wt.%: Carbon ≤0.10, chromium 32.0-35.0, tungsten 4.3-5.30, molybdenum 2.3- 3.3, aluminum 0.5-1.10, titanium 0.5-1.10, iron ≤4.0, niobium 0.5-1.10, boron ≤0.008, cerium ≤0.030, manganese ≤0.50 , silicon ≤0.40, sulfur ≤0.01, phosphorus ≤0.015, nickel - the rest. Alloy of the brand Sv-KhN50VMTYUB-VI (Sv-EP648-VI), TU 14-1-2234-77.

Alloy Sv-EP648-VI has high resistance and sulfide corrosion in contact with the main material of the blades (alloy ChS 70U-VI). However, surfacing on the base material leads to the formation of hot cracks, especially in the heat-affected zone due to insufficient technological strength of the additive.

The objective of the invention is to increase the technological strength of the alloy during surfacing while maintaining its hardness and resistance to sulfide corrosion during operation of the alloy at high temperatures.

This goal is achieved by the fact that the casting alloy based on Nickel contains components in the following ratio, wt.%:

Carbon ≤0.10

Chrome 32.0-35.0

Tungsten 4.3-5.50

Molybdenum 2.3-3.30

Titanium 0.50-1.10

Aluminum 0.50-1.10

Iron ≤ 4.0

Niobium 0.50-1.10

Boron 0.30-0.55

Cerium ≤0.030

Yttrium 0.03-0.05

Manganese ≤0.50

Silicon ≤0.40

Sulfur ≤0.01

Phosphorus ≤0.015

Nickel Else

It is known that nickel heat-resistant corrosion-resistant alloys contain 11-16 important constituent elements in carefully controlled quantities, which, given their different combinations, give the alloys the most diverse properties. It is known that the occurrence of hot cracks can be prevented using boride eutectic. Hot cracks in the weld metal form when boron is present in very small quantities (hundredths and thousandths of a percent). The addition of 0.3-0.8% boron is sufficient for the formation of boride eutectic and effective prevention of hot cracks. It is known that the tendency to form hot cracks during welding depends on the chemical composition and degree of alloying of the alloys. Usually boron-alloyed alloys are welded with a wire of a composition similar to the base metal (B.I. Medovar et al. Austenitic-boride steels and alloys for welded structures, Kiev: Naukova Dumka, 1970, pp. 23-24, 125-127).

The increase in boron content in the proposed alloy improves its hardness and heat resistance while maintaining its plastic properties, and also helps to resist the formation of hot cracks due to the boride phase formed during surfacing, which favorably suppresses crystallization cracks. In addition, the borides that make up the boride phase contribute to the refinement (purification) of grain boundaries from harmful liquids, harmful impurities, silicon, phosphorus, sulfur and others.

The introduction of yttrium and boron additives into the nickel alloy within the proposed limits increases the technological strength of the alloy and increases its resistance to sulfide corrosion at high temperatures.

The proposed alloy is made of pure charge materials by induction in a vacuum and poured into ceramic forms. Before surfacing, the alloy is subjected to processing to remove the casting peel.

To determine the properties of the proposed alloy, comparative tests of this alloy with a prototype were performed: sulfide corrosion tests, calculation and determination of the critical strain rate of deposited alloys (A cr), microhardness of deposited alloys.

10 мм×17 мм) и термическую обработку.For testing for sulfide corrosion, the proposed alloy and welding wire Sv-EP648VI were deposited on samples from the ChS70U-VI alloy. After surfacing, mechanical processing was performed (the dimensions of the samples with deposited metal -

10 mm × 17 mm) and heat treatment.

A quantitative assessment of the resistance of alloys to the formation of hot cracks was carried out according to the IMET-TsNIICHM method with the calculation and determination of the critical strain rate - A cr.

The chemical composition of the proposed and known (prototype) alloys are shown in table 1. Table 2 shows the results of comparative tests of the proposed and known alloys. It was found that an increase or decrease in wt% of boron and yttrium beyond the proposed alloying limits leads to a decrease in the alloy resistance and the formation of hot cracks.

The results of LUM and X-ray control and metallographic studies carried out after surfacing and heat treatment showed the absence of defects both in the deposited metal and in the heat-affected zone.

The advantage of the proposed alloy is a higher technological strength of the alloy during surfacing while maintaining the level of hardness and resistance to sulfide corrosion.

Claims (1)

Nickel-based casting alloy containing carbon, chromium, tungsten, molybdenum, titanium, aluminum, iron, niobium, boron, cerium, manganese, silicon, sulfur, phosphorus, characterized in that it additionally contains yttrium in the following ratio of components, wt. %: Carbon ≤0.10 Chrome 32.0-35.0 Tungsten 4.3-5.50 Molybdenum 2.3-3.30 Titanium 0.50-1.10 Aluminum 0.50-1.10 Iron ≤ 4.0 Niobium 0.50-1.10 Boron 0.30-0.55 Cerium ≤0.030 Yttrium 0.03-0.05 Manganese ≤0.50 Silicon ≤0.40 Sulfur ≤0.01 Phosphorus ≤0.015 Nickel Else