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Lime, cement and concrete
Published in Arthur Lyons, Materials for Architects and Builders, 2019
The compressive strength of hardened concrete may be estimated in situ by mechanical or ultrasonic measurements. The Schmidt hammer or sclerometer measures the surface hardness of concrete by determining the rebound of a steel plunger fired at the surface. In the pull-out test, the force required to extract a previously cast-in standard steel cone gives a measure of concrete strength. Ultrasonic devices determine the velocity of ultrasound pulses through concrete. Since pulse velocity increases with concrete density, the technique can be used to determine variations within similar concretes. The test gives a broad classification of the quality of concrete, but not absolute data for concretes of different materials in unknown proportions.
Effectiveness of synthetic coolant at 0°C on machining of SS304 with PVD coated TiCN tool to evaluate and compare tool wear and surface finish with conventional machining method
Published in Tribology - Materials, Surfaces & Interfaces, 2023
The TiCN coating over the cemented carbide substrate is obtained through agglomerated and sintered TiCN-based powder, which is of spherical and irregular shape and size of 57 µm (data provided by supplier and also verified in lab) is used in the experimentation. The powder lattice of TiCN is of face center cubic (FCC) and has superior properties of high resistance, high melting point, corrosion resistance and oxidation resistance [25]. Fine grain cemented carbide substrate with 7% cobalt binder and rest tungsten carbide was used as base material for coating of TICN. The average grain size of substrate was 1.3 µm (0.8–1.5 µm range). The fine grain powder of substrate is preferred as it’s having carbide resistance against cutting edge. The coating was deposited on the substrate by means of the physical vapour deposition (PVD) technique (Cathodic ion coating system). The coating process includes the process of heating, etching, layer application of coat and cooling. The substrates were first etched for 20 min by using Ar ions at a pressure of 0.15 kPa. The deposition of coating takes place in a heating chamber kept at 550°C for a time period of 200 min. The chamber is maintained at a pressure of 4 kPa by controlling the flow of Nitrogen gas. The time for deposition of coating over the substrate takes 200 min. The TiCN layer deposited over substrate was 4 µm (measured by 3D confocal microscope). Figure 2 shows the schematic layout of coating process chamber. The morphology of coat was found to be of lenticular shape microstructure and the cross-section pattern of coating was of needle grain type structure. The hardness of the coat surface was measured with Hysitron nanoindentor, and the measured value was 20.9 GPa. Scratch hardness of the coating was performed to confirm the adhesion strength between coating and substrate material and was performed by sclerometer (Zhejiang make) and flaking failure mechanism was observed indicating good adhesion strength, and the measured value of critical load was 47.3 N. The surface average roughness of the coat measured with surface roughness tester (make – Mitutoyos) was 0.16 µm The residual stresses developed during coating were measured by XRD, the measured value was −1892 MPa. The XRD pattern of the coating indicates the intensities of Titanium, and carbonitride element atomic weight as 56% and 44%. The initial setting parameter were Bragg angle (2ϴ = 80°), X-ray constant value – 12,000 ksi, and was measured along the plane {200}. The cutting tool insert CNMG 120605 (Kennametal) was used for machining. The test was performed thrice for all the above-measured values, and the average values obtained were in error less than of 3%.