Effect of the Microwave Heating on Diffusion Kinetics and Mechanical Properties of Borides in AISI 316L
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ORIGINAL ARTICLE
Effect of the Microwave Heating on Diffusion Kinetics and Mechanical Properties of Borides in AISI 316L Safiye Ipek Ayvaz1
•
Ibrahim Aydin2
Received: 4 March 2020 / Accepted: 10 August 2020 The Indian Institute of Metals - IIM 2020
Abstract In this study, the effect of microwave heating on boride formation and diffusion kinetics in 316L stainless steel alloys was investigated. Boriding was carried out in microwave furnace with 2.9 kW power and 2.45 GHz frequency. Four different boriding temperatures (800, 850, 900 and 950 C) were used. Boriding was performed for 2, 4 and 6 h for each temperature. Boron layer thicknesses of boride layers were determined by optical microscope. SEM images were taken from the cross sections of the borided samples. Boron activation energy was determined as 244.15 kJ/mol in microwave environment. Two times thicker boride layer was obtained by microwave boriding process compared to the conventional heating process. The mechanical properties of the boride layers formed by microwave boriding (Young’s modulus, hardness, yield strength, residual thermal stress) were determined by nanoindentation tests. Keywords Microwave heating Diffusion kinetic Young’s modulus Nanoindentation 316L Boriding
1 Introduction In the boriding process, which is a thermochemical surface hardening method, boron atoms are thermochemically diffused to the metal surface. Boriding of ferrous alloys is & Safiye Ipek Ayvaz [email protected]; [email protected] 1
Turgutlu Vocational School, Celal Bayar University, 45140 Manisa, Turkey
2
Vocational School of Manisa Technical Sciences, Celal Bayar University, 45140 Manisa, Turkey
usually carried out in the temperature range of 800–1050 C for retention times of 0.5 to 10 h, using boron sources such as solid powder, paste, liquid and gas. As a result of boriding of the ferrous alloys, hard boride layers (FeB/Fe2B) are formed. The hardness of the ferro-boride layer varies from 1200 to 2200 HV0.1 depending on the alloy elements. Thanks to the boride layers formed by boriding, the tribological properties and corrosion resistance of steel alloys can be improved. Boriding can be successfully applied to many steel alloys such as carbon steel, low alloy-steel, tool steel and stainless steel [1–5]. ¨ zdemir et al. borided AISI 316 (SS) alloy at 800, 875 O and 950 C for 2, 4 and 8 h with pack boriding method using Ekabor boriding powders. As a result of diffusion kinetics studies, boron activation energy for AISI 316 SS alloy was determined as 199 kJ/mol [6]. Campos-Silva borided AISI 316 SS alloys at 850, 900, 950 and 1000 C for a period of time ranging from 2 to 10 h. The thickness values of the boride layer obtained by boriding process ranged from 5.07 ± 0.34 to 94 ± 2 [7]. Chegroune et al. borided AISI 316 SS alloy with plasma paste boriding method at 700, 750 and 800 C for 3, 5 and 7 h. As a result of the boriding kinetics studies, boron activation energy was determined as 250.8 kJ/mol [8]. Keddam et al. borided AISI 316 SS alloy
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