Non-ferrous Surfaces Research Articles

Optimization of Surface Roughness of Brass by Burnishing

Abstract—Cylindrical components are important inseveral industrial applications. The surface quality plays a role in part performance. Non-ferrous surfaces are difficultto-finishduetoseveralissuesencounteredingrindingthatis optimum for ferrous metals. Burnishing process, as a metaldeformation process, is believed to be more suitable since iteliminates sticking, wheel dulling and overheating. Themain objective of this work is to optimize the burnishingprocess that can be used to finish the surface of machinedparts. To achieve this, burnishing tool was designed andconstructed in such a way that it can be simply mounted orfixed onto the tool holder of the CNC lathe machine.Experiments are made according to the response surfacemethodology (RSM), in order to improve the reliability ofresults and to reduce the size of the experimental planwithout loss of accuracy. In this work, four burnishingparameters, namely, burnishing speed, feed, depth ofpenetration and number of passes were selected in order tostudy their effects on the surface roughness. Mathematicalmodels, which depend basically on the utilized experimentaldesign, have been developed. Variance of analysis wasconducted to determine the prominent parameters and theadequacy of the models. The results showed that goodsurface roughness can be obtained with minimum cost bytransferring the CNC lathe machine from machine tool tosuper-finishing machine using the proposed burnishing tool.From an initial average roughness of about Ra (4-5 µm), thespecimen could be finished to average roughness of 0.09 µm.

Lubricity of chelated orthoborate-phosphonium ionic liquids on tetrahedral amorphous carbon and steel surfaces

In boundary lubrication, formation of tribofilms and subsequent friction and wear properties are strongly influenced by lubricant affinity to the lubricating surfaces. Ionic liquids (ILs), which are composed of ions, are expected to provide enhanced surface affinity compared to molecular liquids. This is also of interest for non-ferrous surfaces such as diamond-like carbon (DLC) coatings. DLC technology is widely utilised for sliding components, but DLC performance with conventional lubricants does not always fulfil the requirements. In this study, we compare lubricating performance of two non–halogenated ILs with a common cation, trihexyl(tetradecyl)phosphonium, but different anions, bis(oxalato)borate and bis(mandelato)borate, in the steel/steel and steel/DLC contacts. The tribofilms formed and their lubrication mechanism are investigated using a wide range of surface analysis techniques: Atomic Force Microscopy (AFM), nano-indentation, SEM-EDX and X-ray Photoelectron Spectroscopy (XPS). It is demonstrated that both ILs exhibited better lubricating performance than PAO oils of similar viscosity. It is also shown that the lubricating performance is controlled by the chemical stability of ILs, surface hardness and topography. The phosphonium bis(oxalato)borate IL exhibited excellent lubricity but its performance was adversely affected by the rough and very hard DLC surface that disrupted a delicate balance between the rates of tribofilm formation and removal. A higher chemical stability of the phosphonium bis(mandelato)borate IL facilitated formation of a non-sacrificial ionic tribofilm that reduced friction to a lower extent than the phosphonium bis(oxalato)borate IL but without accelerated tribochemical wear. The results demonstrate the potential for controlling lubrication properties by tuning functional groups of anion structure and subsequent chemical reactivity of ILs with lubricated surfaces.

INTERACTION OF NOVEL LUBRICANT ADDITIVES BASED ON MoS2 NANOTUBES WITH NON-FERROUS TRIBOLOGICAL MATERIALS

MoS2 nanotubes (NTs) are novel lubricant additives reducing friction and wear of mechanical components made of steel. Nowadays, non-ferrous surfaces are becoming more widely used, mainly as multifunctional coatings working in configuration with a steel pair. As a consequence, the purpose of this work is to reveal the interaction mechanism of nanoparticles with coated elements in lubricated contacts that are essential in future lubrication technologies. The tribological properties were investigated using a reciprocating sliding testing machine in a steel-ball-on-coated-disc configuration. For tribological studies, two commercially available coatings were selected: WC/C and DLC coating. Frictional results show only slight improvement for lubricant blends containing MoS2 nanotubes with selected coatings, and wear tracks are surprisingly very extensive when compare to oils with additives. Generally, the presence of coating in any tribological test configurations diminish the effectiveness of MoS2 NTs when compare to steel/steel contact. Chemical analytics show that interaction mechanisms of the nanotubes and surface changes, depending on the coating material, have the ability to form a chemically derived tribofilm.

Wear Mechanisms of Hydrogenated DLC in Oils Containing MoDTC

Diamond-Like Carbon (DLC) coatings are well known for offering excellent tribological properties. They have been shown to offer low friction and outstanding wear performance in both dry and lubricated conditions. Application of these coatings for automotive components is considered as a promising strategy to cope with the emerging requirements regarding fuel economy and durability. Commercially available oils are generally optimised to work on conventional ferrous surfaces and are not necessarily effective in lubricating non-ferrous surfaces. Recently, the adverse effect of the Molybdenum DialkyldithioCarbamate (MoDTC) friction modifier additive on the wear performance of the hydrogenated DLC has been reported. However, the mechanisms by which MoDTC imposes this high wear to DLC are not yet well understood. A better understanding of DLC wear may potentially lead to better compatibility between DLC surfaces and current additive technology being achieved. In this work, the wear properties of DLC coatings in the DLC/cast iron (CI) system under boundary lubrication conditions have been investigated to try to understand what appears to be a tribocorrosion-type process. A pin-on-plate tribotester was used to run the experiments using High Speed Steel (HSS) plates coated with 15 at.% hydrogenated DLC (a-C:15H) sliding against CI pins or ceramic balls. The lubricants used in this study are typical examples of the same fully formulated oil with and without ZDDP. The friction and wear responses of the fully formulated oils are discussed in detail. Furthermore, Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM) were used to observe the wear scar and propose wear mechanisms. The X-ray Photoelectron Spectroscopy (XPS) analysis was performed on the tribofilms to understand the tribochemical interactions between oil additives and the DLC coating. Nano-indentation analysis was conducted to assess potential structural modifications of the DLC coating. Coating hardness data could provide a better insight into the wear mode and failure mechanism of such hard coatings. Given the obtained results, the wear behaviour of the hydrogenated DLC coating was found to depend not only on the presence of ZDDP in the oil formulation but also on the counterpart type. This study revealed that the steel counterpart is a critical component of the tribocouple leading to MoDTC-induced wear of the hydrogenated DLC.

Tribological effects of polymer surface modification through plastic deformation

The efficacy of using polymers in cylindrical applications depends closely on its surface friction and wear characteristics. In this regard, a surface modification technique through plastic deformation has been implemented. Roller burnishing is commonly used to improve the surface quality of non-ferrous surfaces, but no work showed concern about roller burnishing as a polymer surface treatment process. The objective of the present work is to investigate the influence of burnishing force and burnishing speed on the friction and wear performance of acetal homopolymer and polyurethane under dry and lubricated sliding conditions. The results reveal that the coefficient of friction and wear rate decreased to a minimum value and then increased as higher burnishing force and speed were applied. It was shown that roller burnishing had favourable prospective to be utilized as a valuable polymer surface treatment technique.

Study on the Scratch Hardness and Indentation Hardness of Burnished Poly(Oxymethylene) Surfaces

Scratch resistance of engineering polymers has become increasingly important for diverse industrial applications as scratches may greatly reduce the life cycle of the components. In this article, a new polymer surface treatment method has been introduced to enhance scratch resistance to a single-pass scratching action. Ball burnishing is a postmachining operation based on plastic deformation commonly used for metals and non-ferrous surfaces. It was demonstrated that ball burnishing is capable of enhancing the scratch hardness and indentation hardness of poly(oxymethylene) surfaces with a good correlation between these two properties. SEM investigations suggest that ball burnishing will alter the mode of scratch damage from severe ductile ploughing and brittle cutting deformation to a mild brittle fracture. A simple model has been proposed that separates the scratching action into two parts, the elastic behavior during indentation and the ploughing behavior during the scratching motion. The dense surface layer induced by the ball burnishing impedes the initial indentation, resulting in less ploughing depth during scratching.

Reactively sputtered TiN coatings for tribological applications

The results of tribological studies carried out on TiN sputter-coated ferrous and non-ferrous materials are presented. A disc magnetron system was used to sputter TiN reactively onto samples suitable for standard friction and wear tests. The tests carried out show that thin films of reactively sputtered TiN, typically 5 microm thick, provide good wear protection for ferrous and non-ferrous surfaces subjected to sliding and rolling contacts. Cutting tests with coated cermet tool inserts show that reactive sputtering is also useful for improving the performance of cutting tool inserts. The results obtained suggest that magnetron reactive sputtering can be useful to enhance the wear resistance of finished precision components.

An investigation of the wear of abrasive grains by rubbing on ferrous and non-ferrous surfaces

The wear characteristics of abrasive grains have been extensively studied using stationary grains carrying a load of 1 or 2 lbs. bearing against a disk rotating at approximately 800 r.p.m. Mean wear volume was found to increase linearly with sliding distance. Carbon steel disks gave lower wear rates for the friable grains than the ductile grains while the reverse was found to be true for Waspaloy and stainless steel. The effect of sliding speed on wear rate and coefficient of friction is also discussed.

Kinetics and mechanism of the decomposition of ammonia on nonferrous surfaces

The kinetics of the decomposition of ammonia on copper, Hastelloy C, and Inconel surfaces was determined, and the validity of three proposed kinetic models was tested with the aid of a computer. The data generally support the Ozaki-Taylor-Boudart mechanism for ammonia decomposition. However, surface heterogeneity is shown to have a significant effect upon the analysis.

Symposium on Priming and finishing of Nonferrous surfaces - "Aircraft Finishing"

Symposium on Priming and finishing of Nonferrous surfaces - "Aircraft Finishing"