T. Sampath Kumar

Comparison of TiAlN, AlCrN, and AlCrN/TiAlN coatings for cutting-tool applications

Monolayer and bilayer coatings of TiAlN, AlCrN, and AlCrN/TiAlN were deposited onto tungsten carbide inserts using the plasma enhanced physical vapor deposition process. The microstructures of the coatings were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM micrographs revealed that the AlCrN and AlCrN/TiAlN coatings were uniform and highly dense and contained only a limited number of microvoids. The TiAlN coating was non-uniform and highly porous and contained more micro droplets. The hardness and scratch resistance of the specimens were measured using a nanoindentation tester and scratch tester, respectively. Different phases formed in the coatings were analyzed by X-ray diffraction (XRD). The AlCrN/TiAlN coating exhibited a higher hardness (32.75 GPa), a higher Young’s modulus (561.97 GPa), and superior scratch resistance (LCN = 46 N) compared to conventional coatings such as TiAlN, AlCrN, and TiN.

Metallurgical Characteristics of TiAlN/AlCrN Coating Synthesized by the PVD Process on a Cutting Insert

TiAlN/AlCrN coating was deposited on a tungsten carbide insert, using the plasma-enhanced physical vapor deposition (PEPVD) process. The microstructure of the coating was examined and it was found that the TiAlN/AlCrN coating was uniform, highly dense, and less porous. The different phases formed in the coating were analyzed using the x-ray diffraction. The hardness and scratch resistance were measured using the nanoindentation tester and scratch tester, respectively. TiAlN/AlCrN exhibited higher hardness, higher Young’s modulus, and superior scratch resistance when compared to the conventional coatings, such as TiAlN, AlCrN, and TiN. The surface morphology of the coating was characterized using the atomic force microscope (AFM). The surface roughness was found to be lesser in the TiAlN/AlCrN coating. The TiAlN/AlCrN coating has proved to have better corrosion resistance, compared to the uncoated carbide substrate.

Comparative Evaluation of Performances of TiAlN-, AlCrN- and AlCrN/TiAlN-Coated Carbide Cutting Tools and Uncoated Carbide Cutting Tools on Turning EN24 Alloy Steel

In the present work, the performances of TiAlN-, AlCrN- and AlCrN/TiAlN-coated and uncoated tungsten carbide cutting tool inserts are evaluated from the turning studies conducted on EN24 alloy steel workpiece. The output parameters such as cutting forces, surface roughness and tool wear for TiAlN-, AlCrN- and AlCrN/TiAlN-coated carbide cutting tools are compared with uncoated carbide cutting tools (K10). The design of experiment based on Taguchi’s approach is used to obtain the best turning parameters, namely cutting speed (V), feed rate (f) and depth of cut (d), in order to have a better surface finish and minimum tool flank wear. An orthogonal array (L9) was used to conduct the experiments. The results show that the AlCrN/TiAlN-coated cutting tool provided a much better surface finish and minimum tool flank wear. The minimum tool flank wear and minimum surface roughness were obtained using AlCrN/TiAlN-coated tools, when V=160m/min, f=0.318mm/rev and d=0.3mm.

Investigation of Structure Property Relationship of the Dissimilar Weld Between Austenitic Stainless Steel 316L and Duplex Stainless Steel 2205

Abstract In the present study, the influence of microstructural changes on the mechanical and corrosion properties of the dissimilar weld between austenitic stainless steel (ASS 316L) and duplex stainless steel (DSS 2205) has been examined and reported. The weld joint was fabricated through the use of gas tungsten arc welding process with a nickel enhanced filler metal ER 2209. The microstructural changes observed in the fusion zone such as nucleation of delta ferrite (δ), austenite (γ) reformation, precipitation of intermetallic phases and the formation of coarser ferrite phases in the HAZ have been reported. Also, the mechanical properties of the weldment such as microhardness, impact toughness and tensile properties have been correlated with microstructural changes. Potentiodynamic polarization test results showed a better electrochemical behavior for ASS 316L than with the weldment and the parent metal of DSS 2205. The austenite phase was found to be electrochemically more stable than the ferrite phase in duplex microstructure. On the other hand, achievement of the stress corrosion cracking resistance by the weldment and the parent metal of DSS was found to be excellent, whereas ASS 316L ended with surface fissures.

Investigation of TiAlN coated roller burnishing on Al-(B4C)p MMC workpiece material

ABSTRACT Burnishing avoids the need for super finishing operations after the conventional turning process, to enhance the surface quality. This paper deals with the surface modifications of Al(B4C)p Metal Matrix Composites (MMC) workpiece material after burnishing with a TiAlN coated WC roller. The burnishing speed, lubrication type, burnishing passes, and coating were the input parameters. Surface hardness and roughness after the burnishing were studied. It was found that the coating on the WC roller had enhanced the hardness in the workpiece after burnishing in the case of Al-5 wt.% (B4C)p, under all conditions. The effect of the coating on the work piece surface hardness was not significant with Al-10 wt.% (B4C)p. While burnishing Al-5 wt.% (B4C)p, the minimum surface roughness combined with maximum surface hardness was obtained, during the third pass under dry condition using uncoated rollers. The number of passes to achieve the desired surface conditions reduced, on using coated rollers with kerosene as the lubricant.

Characterization of TiCN coating synthesized by the plasma enhanced physical vapour deposition process on a cemented carbide tool

In the present investigation, Titanium Carbonitride (TiCN) coating was deposited on a cemented carbide substrate, by means of Plasma Enhanced Physical Vapour Deposition (PEPVD) process. The microstructure of the deposited film was characterized using the Scanning Electron Microscope (SEM). Highly dense, less porous and uniformly distributed TiCN coating was observed on the coated surface. X-Ray diffraction analysis was carried out to access the phases present in the coated layer. The scratch resistance and hardness were measured using the scratch tester and Nanoindenter, respectively. The TiCN coating gives higher hardness and superior scratch resistance when compared to the substrate. The surface morphology of the coated film was characterized using the Atomic Force Microscope (AFM) and was found that the surface roughness was lesser for TiCN coating when compared to cemented carbide substrate. The intensified TiCN coating on the substrate will be useful in improving the surface behavior of cemented carbide cutting tool.

Influence of shot peening on surface quality of austenitic and duplex stainless steel

In the present investigation, an attempt has been made to enhance the surface quality of austenitic stainless steel 316L and duplex stainless steel 2205 through shot peening process. The study mainly focuses the surface morphology, microstructural changes, surface roughness and microhardness of the peened layers. Metallography analysis was carried out and compared with the unpeened surface characteristics. As result of peening process, surface recrystallization was achieved on the layers of the peened samples. It was found that shot peening plays significant role in enhancing the surface properties of 316L and 2205. Particularly it has greater influence on the work hardening of austenitic stainless steel than the duplex stainless steel due to its more ductility nature under the investigated shot peening parameters. The findings of the present study will be useful with regard to the enhancement of surface texture achieved through peening.