Influence of the quenching temperature on the phase composition, structure, and wear resistance of 150XHM steel

The influence of the quenching temperature on the quantity of residual austenite, its stability, and its ease of deformational martensitic transformation in 150XHM steel is studied. In the addition, the hardening and abrasive-wear resistance of the steel are studied as a function of the quenching temperature. The dependences of the steel's hardening and wear resistance on the quenching temperature are of opposite form. The drop in hardness with increase in quenching temperature is due to increase in the content of residual austenite. At the same time, the relative ease of deformational martensitic transformation in the metastable residual austenite results in increase in wear resistance and microhardness of the worn surface. © 2013 Allerton Press, Inc

The effect of thickness on the properties of laser-deposited NiBSi-WC coating on a Cu-Cr-Zr substrate

Ni/60WC coatings on copper substrate were placed via laser deposition (LD). A structural study was conducted using electron microscopy and a microhardness evaluation. Two body abrasive wear tests were conducted with a pin-on-plate reciprocating technique. A tool steel X12MF GOST 5960 (C-Cr-Mo-V 1.6-12-0.5-0.2) with a hardness of 63 HRC was used as a counterpart. The following results were obtained: Precipitation of the secondary carbides takes place in the thicker layers. Their hardness is lower than that of the primary carbides in the deposition (2425 HV vs. 2757 HV) because they mix with the matrix material. In the thin layers, precipitation is restricted due to a higher cooling rate. For both LD coatings, the carbide's hardness increases compared to the initial mono-tungsten carbide (WC)-containing powder (2756 HV vs. 2200 HV). Such a high level of microhardness reflects the combined influence of a low level of thermal destruction of carbides during laser deposition and the formation of a boride-strengthening phase from the matrix powder. The thicker layer showed a higher wear resistance; weight loss was 20% lower. The changes in the thickness of the laser deposited Ni-WC coating altered its structure and wear resistance. © 2019 by the authors.Acknowledgments: This work was supported by the state orders of IMP UB RAS on the subjects “Laser”, “Structure”. The authors are grateful to the collective use center “Plastometry” of the Institute of Mechanical Engineering of the Ural Branch of the Russian Academy of Sciences for their help in conducting structural studies

Structure study of laser treated NiBSi/WC coatings on bronze substrate

Metal matrix composite layers like NiCrB-WC on the substrate of bronze C18150 were performed by laser deposition. The influence of layer thickness and operating parameters on the structural characteristics, microhardness, and crack susceptibility were analyzed. Rational technological modes were defined applied to a diode laser.Проведено сравнение металоматричных покрытий вида NiCrB-WC на основе из бронзы С18150, полученных лазерной наплавкой на основе из бронзы CuCrZr. Проанализированы зависимости изменений структурных характеристик, твердости, склонности к образованию трещин от толщины покрытий и технологических параметров. Определены рациональные режимы обработки с использованием диодного лазера

Wear-resistant nickel-based laser clad coatings for high-temperature applications

The effect of high-temperature processing on laser clad Ni-based coatings is studied. Annealing at 1025°C forms thermally stable framework structures with large chromium carbides and borides. As a result, improved hardness and wear resistance of the coating are maintained when heated to 1000°C. Stabilizing annealing also increases the frictional thermal resistance of the NiCrBSi coating. Under high-speed (3.1– 9.3 m/s) sliding friction, when the surface layer temperature reaches about 500 –1000°С and higher, the wear resistance of the coating increases by 1.7 – 3.0 times. The proposed approach to the formation of heat-resistant coatings is promising, in particular, for a hot deformation tool and other components of metallurgical equipment operating under high thermal and mechanical loads. Such products include crystallizer walls of continuous casting machines. For the walls, the development of laser cladding technology for wear-resistant composite coatings on copper alloys is relevant as an alternative to thermal spraying. The cladding of composite NiBSi-WC coatings of 0.6 and 1.6 mm thickness on a Cu-Cr-Zr bronze substrate heated to 200 – 250°C with a diode laser is considered. The presence of boron causes the formation of the W(C, B) carboboride phase, whose hardness is higher than that of WC in the initial powder. Depending on the thickness of coatings and, accordingly, on the duration of heating and the subsequent cooling, the process of secondary carboborides precipitation from the solid solution can be suppressed (in the “thin” coating) or activated (in the “thick” coating). This leads to a higher wear resistance under friction sliding 1.6 mm thickness coating. © 2019, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.Institute of Education Sciences, IES: АААА-А18-118020790147-4Russian Science Foundation, RSF: 19-79-00031АААА-А18-118020190116-6The work was supported by the state orders of IMP UB RAS on the subjects “Laser” and “Structure” №АААА-А18-118020190116-6 and IES №АААА-А18-118020790147-4. The study of the evolution of the structure of NiCrBSi coatings during heating was carried out with financial support from the Russian Science Foundation, grant № 19-79-00031. The structural studies were done on the equipment installed at the Plastometriya Collective Use Center of IES UB RAS