Effect of induction post-heating temperature on the morphology, microstructure and mechanical performance of the heat affected zone in laser-induction hybrid cladding of full-scale rail

Abstract

Abstract In the present work, the laser-induction hybrid cladding technology with induction post-heating (post-LIHC) was utilized to deposit coatings on the full-scale rail surface, and the effects of different induction post-heating temperature on the morphology, microstructure and mechanical performance of the heat affected zone (HAZ) were first in-depth analyzed. Results indicate that with the increase of the average induction post-heating temperature (Ta) in post-LIHC, the microstructure of the HAZ first transforms from the fine acicular martensite structure to the composite structure of martensite and pearlite, then changes to the pure pearlite structure, and finally retransforms to the coarse martensite structure. Especially, the morphology of the “Martensite Zone” (MZ) in HAZ undergoes three remarkable change with Ta increasing: “flat-U-shaped” → “flat-W-shaped” → “vanished” → “flat-V-shaped”. Under the induction post-heating window of Ta = 508 °C ~ 565 °C, not only the MZ in HAZ can be inhibited absolutely, but also fine pearlite with much lower interlamellar spacing, smaller grain size and higher grain misorientation forms instead, making the strength and toughness are both enhanced significantly than the other three type HAZs and the rail substrate. In addition, increasing the induction post-heating temperature within the window of Ta = 508 °C ~ 565 °C can increase the interlamellar spacing and reduce the ferrite grain misorientation of the pearlite structure in HAZ, but has no obvious effect on the grain size therein.