The Corrosion and Wear Behaviors of a Medium-Carbon Bainitic Steel Treated by Boro-Austempering Process

Abstract

The effects of boro-austempering treatment on growth kinetics of borided layers, microstructure, and properties in a medium-carbon bainitic steel were investigated. The microstructure, distribution in coatings, corrosion, and wear properties of boro-austempered steels were characterized by a microscope, field-emission electron probe micro analyzer, scanning vibrating electrode technique system and wear resistance machine. The results show that the corrosion resistance of steels in different corrosive mediums was significantly enhanced by boro-austempering treatment. In addition, the wear performance of borided layers was improved by more than two times compared to bainitic substrates, proving a better wear property of samples treated through the boro-austempering route. The solubility of carbon and silicon in borides is very little. In addition, the dual-phase coating of FeB and Fe2B was observed, and the internal stress induced during the growth of Fe2B and FeB was almost eliminated. The preferential crystallographic growth directions of Fe2B and FeB are [001] and [010], respectively, which belongs to the (100) plane. Finally, the kinetics equation d2 = 0.125·t of the borided layers at 1223 K was established.

The Effect of Hybrid Treatment Combining Boriding and Nanobainitising on the Tribological and Mechanical Properties of 66SiMnCrMo6-6-4 Bearing Steel

“…The formed layers have a thickness of 70.1 ± 4.9 µm. Similar borided layers microstructures were revealed in other works [16,27,31,32]. Below is the substrate of a layer with a martensitic structure resulting from the cooling conditions after boriding.…”

“…The presence of this phase is a typical phenomenon in borided steels. Since silicon atoms hardly dissolve in the crystal lattice of borides, they are pushed by the front of new phase growth [27,30]. Silicon atoms redistribution leads to developing areas with a high silicon concentration that prevents the borides' growth.…”

“…Combining the advantages of boriding and nanobainitising of steel appears worth investigating. In recent years, several research studies dealing with boriding and bainitising have been carried out [25][26][27]; however, they did not concern a carbide-free nanobainite. In addition, these studies focused mainly on the properties of the boride layer.…”

Effect of Prior Boriding on Microstructure and Mechanical Properties of Nanobainitic X37CrMoV5-1 Hot-Work Tool Steel

“…Most of the research to date concerns the optimisation of the boriding process or the characterisation of the produced layers. In the case of isothermal quenching, only a few works dealing with this issue can be indicated [ 23 , 24 , 25 ]. These are relatively new works, breaking the previous trend.…”