Effects of energy density on the mechanical properties, residual stress and thermal-fatigue of Fe-Cr alloy fabricated by laser directed energy deposition

Abstract

Abstract Aiming at the problem that AISI4340, a common material for fully mechanized coal-mining equipment, is prone to wear failure in harsh working environment. To repair damaged area and improve service performance, the high-strength Fe-Cr alloy coatings having different laser energy densities were fabricated on the AISI4340 by laser directed energy deposition. The effects of the energy densities on the tensile properties, hardness, residual stress, wear and thermal-fatigue damage were systematically studied. The models of thermal-fatigue damage and service life were established and improved, and the prediction accuracy were verified. The results indicated that with the increasing energy density, the tensile strength and Rockwell hardness increased first and then decreased, and the residual stress on the coating surface aggrandized with increasing temperature gradient. When the energy density was 35.01 J/mm2, the wear depth and wear rate were 51.8 µm and 1.91×10− 2 mm3∙N− 1∙mm− 1, and the wear resistance was increased by two times compared with the substrate. Considered the effective crack propagation and loading order, the accuracy of the service life models were improved from 65.9% and 23.1–14.6% and 6.7%, respectively. Selecting appropriate energy density is beneficial to improve the mechanical properties and decrease the thermal-fatigue damage of Fe-Cr alloy coatings.