B. Ramamoorthy

A study on the wear resistance of electroless Ni–P/Diamond composite coatings

Abstract The ability to co-deposit particulate matter in a matrix of electroless nickel has led to a new generation of composite coatings. Polycrystalline diamond is one of the many varieties of particulate matter that can be co-deposited. Composite diamond coating is a regenerative layer of fine diamond particles dispersed in a hard electroless nickel matrix. In this work, experiments have been carried out to study the effect of heat treatment, particle size and phosphorus content on the wear characteristics of the composite electroless coating containing diamond particles. The results indicate substantial increase in wear resistance after the coated sample containing 9–10 wt.%. P content having fine diamond particle size is annealed around 350°C.

Statistical approaches to surface texture classification

Abstract With the advent of high speed general-purpose digital computers and vision systems, it is becoming easier to digitize any image and to analyse them for various applications. There are basically three possible approaches for characterizing the textural features from the digitized images: statistical, structural and spectral. Here in this work an attempt is made to characterize some of these features of texture produced by various machining operations, namely grinding, milling and shaping by processing the digital image of the texture pattern using statistical methods.

Performance of TiCN and TiAlN tools in machining hardened steel under dry, wet and minimum fluid application

In this work, an experimental study has been carried out on the comparative performance of TiCN and TiAlN coated tools in machining of AISI 4340 hardened steel under dry, wet and minimum fluid application conditions and the analysis of results are presented. Cutting force, cutting temperature, surface finish and flank wear are compared in all the cases to understand the performance. Then, the relative influences of the machining and the minimum fluid application parameters on the machining performance of tools have been analysed and presented in this paper.

An Investigation into the Adhesion Strength of Diamond Like Carbon Multilayer Coating (DLC/TiN/Ti/Cu/Ni)

Advancement in vacuum technologies and vapor deposition processes during last decades has led to the introduction of many modern coatings on metal cutting tools. Even in such an advanced vacuum coating techniques, the failure is not due to the wear of the coating but rather due to the lack of coating adhesion to the substrate. In this work, the coating adhesion test results were performed which is based on the Rockwell indentation tests. This coating adhesion tests were performed as per VDI standards 3198, 1991 for d.c. magnetron sputter deposition of diamond like carbon multilayer coating (DLC / TiN/ Ti / Cu / Ni) on tool substrate. Multilayer coating was deposited on tool substrates at different sputtering parameters/conditions such as power density, partial pressure, substrate temperature and reactive gases. The coated multilayer films were characterized by experimental techniques such as X-ray diffractometer which measures the material deposited, micro Raman spectroscopy and TEM to check DLC, Rockwell indentation to examine adhesion strength, optical profilometer to measure thickness of coating. Ni increases the Cu adhesion on tool substrate. Cu accommodates the shear stress induced by the films / substrate and the mismatch in thermal expansion coefficient, while Ti and TiN promote better DLC bonding. As the target power was increased the adhesion strength, micro hardness and deposition rate were observed to improve. Increase in target power and substrate temperature enhances adhesion strength. Proper substrate preparation and sequence of cleaning processes are the crucial factors for the enhancement of adhesion strength. The sputter deposition conditions for the above mentioned multilayer coatings are identified in this work to get improved quality with particular reference to adhesion and surface finish.

Influence of surfactants on the tribological behaviour of electroless Ni?P coatings

Electroless nickel?phosphorus coating has been deposited onto plain carbon steel specimens by using an alkaline bath based on NiCl2 as source of nickel cations. The tribological behaviour under dry non-lubricated conditions has been evaluated by employing the pin-on-disc test method. Two surfactants namely sodium dodecyl sulphate and cetyl trimethyl ammonium bromide were added to the EN bath for the first time in the similar kind of study. The influence of the surfactants on the hardness, friction and wear behaviour of the coatings was investigated and compared against the samples produced without addition of surfactants.

Study on characterisation and influence of surfactants on adhesion and coating thickness of electroless Ni–P deposits

Electroless nickel–phosphorus (EN) deposits with and without addition of surfactants were made on mild steel substrates. Two surfactants namely sodium dodecylsulfate (SDS) and cetyltrimethyl ammonium bromide (CTAB) were used in the study. The EN coated samples were characterized using X–ray diffraction analysis and transmission electron microscopy. The XRD pattern of all the deposits indicated the presence of crystalline and amorphous phases coexisting in the as deposited condition. Profile refinement techniques have been used to separate the crystalline nickel (111) reflection from the amorphous profile. The crystallite size of nickel was found to vary from 200 nm in the as deposited condition to 80 nm with addition of surfactant. TEM study reveals a nano crystalline structure of the deposit in as plated condition and an amorphous structure with addition of surfactants. With addition of surfactants adhesion was good. The coating thickness varied from 12.7 µm to 32.2 µm with addition surfactants.

Measurement of surface finish using an optical diffraction technique

In recent years there has been considerable growth in the use of optical methods for evaluating surfaces. Conventional stylus techniques, though powerful, have their own limitations. These include the resolution of the stylus, and the damage caused by the moving diamond stylus when tracing profiles on soft materials. Hence non-contact methods of measuring surface finish of often required. One approach in this direction is the use of an optical diffraction technique. The unique properties of the diffraction phenomenon make this technique useful and the validity of this technique in the evaluation of surface finish is investigated in this paper.

A study of the surface deformations in press and shrink fitted assemblies

Abstract The load-bearing capacity of press and shrink fitted assemblies depends largely on the surface finish of the mating surfaces, which influences the contact area and, in turn, the contact pressure of the assemblies. The role played by the surface profiles can be best explained if it is possible to know how the profiles modify after assembly. This paper deals with the experimental investigations made to obtain the surface deformation details in shrink and press fits and their effects on the strength of the assemblies are discussed.

Influence of minimum quantity lubrication on the high speed turning of aerospace material superalloy Inconel 718

Superalloy, Inconel 718 is termed as ‘difficult to cut’ material due to its poor machinability. In order to effectively take advantage of inherent properties such as high temperature resistance, corrosion resistance, creep resistance, and high strength to weight ratio and longer operational life of Inconel 718, it is necessary to improve its machinability. Hence, researchers and industry are working to explore the machinability characteristics of this material particularly with respect to high speed machining (HSM). In these investigations machinability characteristics of Inconel 718 under dry and minimum quantity lubrication (MQL) conditions were evaluated with respect to cutting forces, surface roughness and tool wear using K20 tungsten carbide cutting tool. Moreover, X-ray diffraction analysis of the collected chips was carried out to study the direct effect of dry and MQL cutting conditions to confirm the experimental results obtained. It was observed that machining of Inconel 718 under MQL condition ...

Identification of defects on highly reflective coated ring components using dark field illumination and image segmentation using simple thresholding technique

This paper deals with inspection of highly reflective chrome coated rings used in textile machinery using machine vision. These rings are mass produced in very large numbers in a textile machinery manufacturing company and the inspection was carried out manually using optical methods. Introduction of automated vision inspection had not helped the industry fully to achieve 100% quality inspection. Moreover, the whole procedure had to be made quicker in view of the number of components manufactured which is of the order of hundreds of thousands and to be inspected 100% thereafter. Also in order to improve inspection speed and to ensure 100% quality inspection, it was absolutely essential to improve the complete inspection process. Also a proper sorting algorithm was to be considered to classify defective and non-defective components. The effect of curvature, reflective nature of material and the real-time inspection make the imaging and defect detection and classification difficult. The use of dark field illumination has been tried out in this work to quicken the process of defect detection and also to improve the accuracy of detection. The images of the defects captured using a CCD camera of the inner and outer surfaces of the coated ring components have been analysed. The images were subjected to a simple thresholding technique to segment out defects, thus avoiding the use of complex image processing algorithms. It was observed that the classification of defects using dark field illumination was very effective for this particular case and the results as well as analysis of the same are presented in this paper.