Influence of Rapid Cooling Rate and Homogenization Temperature on the Ferrite Content and Microstructures of CD3MWCuN Ca
- PDF / 4,502,057 Bytes
- 9 Pages / 593.972 x 792 pts Page_size
- 27 Downloads / 155 Views
LEX stainless steels (DSSs), which consist of a 50/50 mixture of austenite (c) and ferrite (d), are extensively used in a variety of applications including marine, oil, pulp, and petrochemical industries due to their excellent mechanical properties and corrosion resistance.[1–3] Duplex stainless steels (DSS) are well known due to their high mechanical properties and good stress-corrosion cracking resistance which may replace standard austenitic stainless steels in some industrial applications.[4–6] Duplex stainless steel alloys have been heavily studied in the past. Studies have shown that the mechanical properties, solidification cracking resistance, and corrosion resistance are influenced by the amount of secondary phase formation.[7,8] Mo is added to DSS to improve the resistance to crevice and pitting corrosion. Recent studies have shown Mo, in combination with N, improves the selective dissolution of iron at the surface and causes Cr enrichment under the passive film.[9]
LONGLONG LIAO and SCOTT CHUMBLEY are with the Department of Material Science and Engineering, Iowa State University, Ames, IA 50010. Contact e-mail: [email protected] Manuscript submitted September 9, 2018. Article published online February 23, 2019 2322—VOLUME 50A, MAY 2019
The exposure of DSS between 600 °C and 1000 °C will induce intermetallic phase formation such as sigma and chi phase.[10–12] Sigma, rich in Cr and Mo reduces corrosion resistance and toughness by removing these critical alloying additions from the matrix.[13] It was reported that sigma phase can be formed by three different mechanisms at 850 °C: nucleation and growth from original ferrite, eutectoid decomposition of ferrite, and growth from austenite after total consumption of original ferrite.[14–16] Sigma phase turns out to be the most common intermetallic formed during cooling.[17] It is well known that the ferrite content of duplex stainless steels can be influenced significantly by the compositions.[18–20] There are more than ten elements in this steel classified as ferrite stabilizers (Cr, Mo) or austenite stabilizers (Ni, N, C, Mn, Cu).[7–9] However, the effect of cooling rate and homogenization temperature on determining the ferrite content in cast alloys is not well known. In this paper, the influence of rapid cooling rate and homogenization temperature on the microstructures and ferrite content of CD3MWCuN casting will be investigated. The objective of this research is to understand how the homogenization temperature and cooling rates affect the microstructure and phase percentage of CD3MWCuN castings. The CD3MWCuN casting was selected because of its relatively high Cr, Mo and Ni concentration which makes its highly corrosion resistance and typical use in industry. The ferrite, austenite and intermetallic percentage will be measured by point-count method using BSE-SEM images. The result of this work is useful for METALLURGICAL AND MATERIALS TRANSACTIONS A
designing heat treatments that can achieve a desired ferrite percentage for CD3MWCuN castings.
II.
often difficu
Data Loading...
