Microstructure and Mechanical Properties of Borided Inconel 625 Superalloy

Abstract

The Ni- based superalloy Inconel 625 is extensively used owing to its high strength, excellent fabricability,
good weldability and outstanding resistance to high temperature corrosion against aggressive environments.
However, despite its unique properties and extensive use, its wear resistance is in some cases unsatisfactory.
In this study, Inconel 625 was subjected to boriding treatments at different temperature and different
durations. Microstructural characterization was made by conventional methods (scanning electron
microscopy, optic microscopy, X-ray diffraction analysis) and mechanical characterization was made by
microhardness and micro-abrasion wear test. Micro-abrasion wear tests were conducted against a AISI 52100
steel under 5, 7.5 and 10 N load in a 25 wt.% SiC slurry at room temperature. Microstructural results
revealed that multi-phase boride layer (nickel boride, chrome boride and iron boride) and silicide layer were
formed. The hardness and thickness of the boride layers were found to be 1175--2432 HV0.1 and, 6.61 -- 92.03
μm, respectively. Depending on the boriding temperature and time. In spite of silicide layer formation the
wear resistance of borided Inconel 625 alloy increased up to 8 times thanks to the increase in the surface
hardness which was caused by boriding process. The boriding treatment caused a transition in the wear
mechanism. While grooving was observed in the untreated Inconel 625 samples, mixed (grooving and
rolling) and rolling type wear was predominant in the borided samples.