Investigation on structural and tribological properties of borided gear steel after phase homogenization


Arslan M. , Ok A. C. , Kartal Şireli G. , Timur S.

SURFACE & COATINGS TECHNOLOGY, vol.429, 2022 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 429
  • Publication Date: 2022
  • Doi Number: 10.1016/j.surfcoat.2021.127967
  • Title of Journal : SURFACE & COATINGS TECHNOLOGY
  • Keywords: Boriding, CRTD-Bor, Fe2B, AISI 8620, Gear steel, Wear, Phase homogenization, ABRASIVE WEAR BEHAVIOR, AISI 8620 STEEL, KINETICS, LAYERS, EVOLUTION, HARDNESS, GROWTH, CARBON

Abstract

This study focused on the structural and mechanical characterizations of AISI 8620 gear steel after a novel combined treatment (CRTD-Bor: Cathodic Reduction and Thermal Diffusion based boriding and subsequent PH: phase homogenization). Initially the effects of CRTD-Bor process parameters on the modified layer depth and chemistry were investigated at two sets of experiments as follows i) temperature examinations-15 min of CRTDBor at 950, 1000, 1050 and 1100 degrees C ii) duration investigations - at 950 degrees C for 15, 30, 60 and 120 min of CRTDbor. After that, PH treatment was integrated into CRTD-Bor to obtain industrially-desired monolithic Fe2B coatings. The optimized parameter of the dual treatment was found as 15 min of CRTD-Bor and subsequently 45 min of PH at 1000 degrees C, which resulted in 100 mu m thick sole Fe2B layer having 1600 +/- 100 HV hardness along with the perfect adhesion-HF1 quality. The tribological properties were evaluated by sliding wear tests in pin-on-disc configuration under dry and lubricated conditions. Since the wear in gear systems is of concern, wear tests were conducted to unborided pin/unborided disc, borided pin/unborided disc and borided pin/borided disc tribocouples. For both environments, the unborided tribo-pairs exhibited the highest loss whereas the borided tribo-couples had no measurable wear. Results of tribological tests revealed that the combined treatment successfully improved the wear resistance of the gears working in relative motions.