Microstructure and Mechanical Properties of Borided Inconel 625 Superalloy

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 differentdurations. Microstructural characterization was made by conventional methods (scanning electronmicroscopy, optic microscopy, X-ray diffraction analysis) and mechanical characterization was made bymicrohardness and micro-abrasion wear test. Micro-abrasion wear tests were conducted against a AISI 52100steel under 5, 7.5 and 10 N load in a 25 wt.% SiC slurry at room temperature. Microstructural resultsrevealed that multi-phase boride layer (nickel boride, chrome boride and iron boride) and silicide layer wereformed. The hardness and thickness of the boride layers were found to be 1175--2432 HV0.1 and, 6.61 -- 92.03μm, respectively. Depending on the boriding temperature and time. In spite of silicide layer formation thewear resistance of borided Inconel 625 alloy increased up to 8 times thanks to the increase in the surfacehardness which was caused by boriding process. The boriding treatment caused a transition in the wearmechanism. While grooving was observed in the untreated Inconel 625 samples, mixed (grooving androlling) and rolling type wear was predominant in the borided samples

Determination of Barreling of Aluminum Solid Cylinders During Cold Upsetting Using Genetic Algorithm

This study presents Genetic Programming models for the formulation of barreling of aluminum solid cylindersduring cold upsetting based on experimental results. The maximum and minimum radii of the barreledcylinders having different aspect ratio (d/h= 0.5, 1.0 and 2.0) were measured for various frictional conditions(m=0.1-0.4). The change in radii with respect to height reduction showed different trends before and afterfolding, therefore, the corresponding reduction ratios of folding were also determined by using incrementalupsetting. Genetic programming models were prepared using the experimental results with the input variablesof the aspect ratio, the friction coefficient, and the reduction in height. The minimum and maximum barrelingradii were formulated as output taking the folding into consideration. The performance of proposed GP modelsare quite satisfactory (R2 = 0.908-0.998).Keywords: Upset, forging, barreling, bulging, axisymmetric compression

Dry sliding wear behavior of bonded hot-work tool steel at elevated temperatures

In the present study, the surface of AISI H13 hot-work tool steel was bonded with EKabor II powders using powder pack-bonding method. The process was carried out at 800,900 and 1000 degrees C temperatures for 2,4 and 6 h periods. The wear tests were carried out using a ball-on disc tribometer at room temperature and 500 degrees C on bonded and untreated AISI H13 hot-work tool steel. Scanning electron microscope (SEM), optical microscope, 3D profilometer, X-ray diffraction analysis and micro-hardness tester were used in the evaluation of micro-structure and wear data. The increase in the bonding temperature and bonding period led to increased thickness and hardness of the boride layer. Bonding at 800 degrees C resulted with formation of Fe2B, Mn2B, Cr5B3, phases, while FeB, Fe2B, Mn2B, and Cr5B3 boride phases occurred at 900 and 1000 degrees C. Dominant wear mechanisms were microcrack-induced plastic deformation during high temperature wear tests; oxidation and microcrack formation during room temperature wear tests; and oxidation and severe plastic deformation for the untreated specimen. (C) 2017 Elsevier By. All rights reserved

A Comparative Study on the Effects of Different Thermochemical Coating Techniques on Corrosion Resistance of STKM-13A Steel

The corrosion resistances of three different thermochemical coatings (grown using titanizing, boriding, and borotitanizing treatments) applied to STKM-13A steel surfaces were investigated. The coatings were characterized using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, 2D profilometry, and microhardness experiments. The corrosion tests were conducted using both electrochemical and static immersion methods, in 3.5 pct NaCl and 40 pct HF acid solutions, respectively. The corrosion resistance of STKM-13A steel was enhanced after the coating process. The specimens were exposed to more corrosion in the HF solution than in the NaCl solution. The best corrosion resistance was obtained in the borotitanized and borided specimens immersed in the NaCl and HF solutions, respectively. The borided STKM-13A steel sample showed even less cumulative weight loss than Inconel 625 in the static immersion HF acid solution test. This suggests potential use of the borided STKM-13A steel in the uranium production units of nuclear power plants as an alternative to more costly alternatives such as Monel, Inconel, and Hastelloy. (C) The Minerals, Metals \& Materials Society and ASM International 201