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KR-102962322-B1 - High-temperature Fe-based Alloy Powder and Sintered Body Using the Same

KR102962322B1KR 102962322 B1KR102962322 B1KR 102962322B1KR-102962322-B1

Abstract

The present invention aims to provide a heat-resistant steel powder for powder metallurgy that has high-temperature oxidation resistance and heat resistance properties capable of withstanding temperatures of 1,000°C or higher while minimizing or not including the expensive Co content. To achieve the above objective, according to the present invention, an Fe-based alloy powder for high-temperature components can be provided, comprising 18-22 wt% chromium (Cr), 25-35 wt% nickel (Ni), 1-2.5 wt% silicon (Si), 1-5 wt% aluminum (Al), 2-4 wt% niobium (Nb), and 0.2-0.5 wt% carbon (C), with the remainder consisting of iron (Fe) and other unavoidable impurities, having an average diameter of 7-80 μm and an aspect ratio of 1-1.5.

Inventors

  • 이언식

Assignees

  • 포항공과대학교 산학협력단

Dates

Publication Date
20260507
Application Date
20231016

Claims (9)

  1. It comprises 18–22 wt% chromium (Cr), 25–35 wt% nickel (Ni), 1–2.5 wt% silicon (Si), 1–5 wt% aluminum (Al), 2–4 wt% niobium (Nb), and 0.2–0.5 wt% carbon (C), with the remainder consisting of iron (Fe) and other unavoidable impurities, The average diameter is 7–80 µm, and the particle aspect ratio is 1–1.5, Fe-based alloy powder for high-temperature components, further comprising only one of 0.15 to 0.25 wt% nitrogen (N) or 5 to 10 wt% cobalt (Co).
  2. In Article 1, The above Fe-based alloy powder is an Fe-based alloy powder for high-temperature components having an average diameter in the range of 7 to 20 μm.
  3. In Article 1, Fe-based alloy powder for high-temperature components comprising 30-35 wt% nickel (Ni), 2.0-2.5 wt% silicon (Si), 1-3 wt% aluminum (Al), 2.2-3.0 wt% niobium (Nb), and 0.24-0.33 wt% carbon (C).
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  7. In Article 1, The above Fe-based alloy powder is a raw material powder for high-temperature parts, which is used in metal injection molding, additive molding, or high-temperature isostatic pressing processes.
  8. Made using Fe-based alloy powder according to any one of claims 1 to 3 and 7 through a metal injection molding, additive molding, or high-temperature isotropic pressing process, and Fe-based alloy powder sintered body having a high-temperature tensile strength in the range of 65 to 95 MPa at 1,000℃.
  9. In Article 8, The above sintered body is an Fe-based alloy powder sintered body having a microstructure at 1,000°C consisting of an austenite matrix structure and an MC carbide precipitate phase, wherein the volume fraction of the MC carbide is 2 to 5%.

Description

High-temperature Fe-based alloy powder and sintered body using the same The present invention relates to a high heat-resistant steel material usable in a 1,000°C environment, and to an Fe-based alloy powder having low cost and high high temperature characteristics, and a sintered body using the same. A turbocharger is a device designed to increase power output by utilizing the pressure of exhaust gases, which are inevitably generated by internal combustion engines, to rotate a turbine. This rotational force is then used to force intake air into the engine at a pressure higher than atmospheric pressure. Although this technology was originally developed for aircraft engines, it is now primarily used in automobile engines. Turbochargers installed in diesel engines have a relatively simple structure and design, so most recently mass-produced diesel vehicles are equipped with them; however, demand for diesel turbocharged engines is plummeting due to environmental regulations. Conversely, as the global demand for fuel-efficient vehicles grows and downsizing becomes a trend, the use of turbochargers in gasoline and hybrid vehicles has been rapidly increasing recently. In the case of diesel turbocharged engines, combustion generally occurs under an air-excess state with a fuel-to-air supply ratio of approximately 1:20 or higher, resulting in exhaust gas temperatures of up to about 850°C. On the other hand, gasoline turbocharged engines have a theoretical fuel-to-air mixture ratio of about 1:14.5, which is higher than that of diesel engines, leading to exhaust gas temperatures of approximately 1,050°C. Due to these differences in operating environments, gasoline engine turbochargers must utilize high-heat-resistant steel materials capable of operating in environments of at least 1,000°C to cope with high exhaust gas temperatures. As exhaust gas regulations become stricter in the future, exhaust temperatures for gasoline engine turbochargers are expected to rise further; therefore, it is predicted that the development of heat-resistant steel materials capable of operating in 1,050°C environments will be necessary for these applications. Looking ahead, the demand for diesel engine turbochargers is expected to plummet due to environmental regulations, while the demand for gasoline engine turbochargers is projected to steadily increase until 2050, when internal combustion engine vehicles are expected to remain in operation. Furthermore, the European Union (EU) Commission, which decided to ban the registration of new internal combustion engine vehicles starting in 2035, has decided to grant an exception for internal combustion engine vehicles using e-fuel. This decision is based on the judgment that e-fuel vehicles contribute to achieving carbon neutrality. E-fuel is a renewable synthetic fuel made from liquid fuel produced using green hydrogen ( H₂ ) obtained by the electrolysis of water and carbon dioxide ( CO₂ ) from the air. Since e-fuel does not increase carbon emissions, even if it cannot reduce them, it is essential for achieving carbon neutrality in the future. According to the International Energy Agency (IEA)'s carbon neutrality scenario, the proportion of internal combustion engine vehicles will reach 60% of the total by 2050. In addition, aircraft, large ships, and large trucks also pose a hurdle. Due to the nature of these modes of transportation requiring long-distance operation, it is difficult to achieve the efficiency levels of liquid fuel using battery-powered systems. For these reasons, it is predicted that battery electric vehicles, hydrogen electric vehicles, and e-fuel internal combustion engine vehicles will coexist as eco-friendly vehicles in the future. Currently, HK-30 heat-resistant steel alloy powder, which can be used at an exhaust temperature of 800°C, is mainly used for turbocharger parts for diesel engines, whereas there is still no effective commercial alloy powder for turbocharger parts for gasoline engines that generate exhaust temperatures of 1,000°C or higher. Furthermore, to improve the efficiency of e-fuel internal combustion engines, it is necessary to develop heat-resistant steel materials for turbocharger components that can be used at temperatures exceeding 1,050°C. Currently, DIN 1.4957 alloy powder is being used experimentally as a heat-resistant steel alloy applicable to exhaust temperatures above 1,000°C. However, DIN 1.4957 powder has the problem of very high manufacturing costs due to its content of 20% Co and 20% Ni. In particular, M₂³C₆ and M₇C₃ carbides generated by the addition of W and Mo grow rapidly at high temperatures above 1,000°C, which can adversely affect the high-temperature lifespan of the components. Since the exhaust temperatures of turbochargers for gasoline and e-fuel internal combustion engines are planned to rise to 1,050°C in the future, it is necessary to develop heat-resistant steel powders designed with a new concept suitable for manufacturing powd