Accession Number:

ADA585615

Title:

Friction Stir Welding of HT9 Ferritic-Martensitic Steel: An Assessment of Microstructure and Properties

Descriptive Note:

Master's thesis

Corporate Author:

NAVAL POSTGRADUATE SCHOOL MONTEREY CA

Personal Author(s):

Report Date:

2013-06-01

Pagination or Media Count:

115.0

Abstract:

This thesis explores the processing-microstructure-property relationships in friction stir welded FSW HT9A ferritic-martensitic steel. HT9 has previously been studied as a structural component for fusionfission based reactors however, the changes in material microstructure and properties after friction stir welding have not been considered. HT9A steel plate was friction stir welded with a series of increasing heat inputs. The microstructure of this welded material was characterized using optical and electron microscopy. The mechanical properties of the welded material were determined using nanoindentation and microhardness measurements. In addition, electrochemical impedance spectroscopy EIS in molten lithium fluoride was used to assess the high temperature corrosion resistance of the welded material in the harsh environments found in fusion reactors. The quality of the friction stir welds was excellent, and the basic ferritic-martensitic microstructure was maintained for all of the conditions used. Some reduction in hardness was observed in the welded material, particularly in the heat affected zones. The high temperature corrosion response of the welded material was comparable to, or slightly better than, the base plate material.

Subject Categories:

  • Metallurgy and Metallography
  • Fabrication Metallurgy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE