The effect of the heat-affected zone created by laser-surface alloying on the high-cycle fatigue behavior of AISI 4340 steel

Author

Robert L. McDaniels, University of Tennessee

Date of Award

5-2002

Degree Type

Thesis

Degree Name

Master of Science

Major

Materials Science and Engineering

Major Professor

Peter K. Liaw

Abstract

The high-cycle fatigue behavior of a CrB2-coated AISI 4340 steel subjected to four-point-bend fatigue experiments is discussed. Samples of AISI 4340 steel from several different lots were coated with CrB2 by a laser-surface-alloying (LSA) process. The samples were then subjected to four-point-bend, high-cycle-fatigue testing. The experiments were run to failure at an R ratio of 0.1, where R = σmin/σmax, σmin and σmax being the minimum and maximum applied stresses, respectively. The failed samples were then subjected to Scanning Electron Microscopy (SEM) and metallography. For the Lot 1 and Lot 2 material showed slightly improved fatigue performance at some stress levels, but for the Lot 4 samples, the laser coating proved to be detrimental to the fatigue performance of the alloy. Microhardness measurements as a function of the depth from the coating surface were taken for each lot of material. The difference in fatigue performance between the various lots was explained in terms of the fracture mechanisms, microstructures, and hardness differences resulting from the LSA process.

Recommended Citation

McDaniels, Robert L., "The effect of the heat-affected zone created by laser-surface alloying on the high-cycle fatigue behavior of AISI 4340 steel. " Master's Thesis, University of Tennessee, 2002.
https://trace.tennessee.edu/utk_gradthes/5961