Surface Layer Of Parts Research Articles

Formation of roughness of the surface layer of non-rigid parts of hollow cylinder type during combined machining and surface plastic deformation

The forming of surface roughness of non-rigid parts such as hollow cylinder while combined machining intervenes three phases. The magnitude of surface roughness depends on shape and size of deformed elements, magnitude of axial feed, radial forcing, number of stressing cycles, physical and mechanical parameters of the material, etc.

Ensuring the quality of the surface layer of parts in the processing of surface plastic deformation

У статті розглядаються питання підвищення надійності та довговічності деталей машин за рахунок підвищення якості їх поверхневого шару при різних способах обробки.

A Model of Forming the Surface Layer of Ceramic Parts Based on Silicon Nitride in the Grinding Process

The results of the study of the influence of the grinding regimes and the characteristics of the diamond tool on the strength and the surface layer of the ceramic parts based on silicon nitride are presented in this article. The revealed regularities of the surface layer and defect formation have been used to develop a model of the forming of the surface layer of the ceramic parts. The proposed model will increase operational resource resistance of the ceramic parts by 10–25%.

Composite Layers with Ceramic Matrix Modified with Glassy Carbon Destined for Oil-Less Sliding Pairings

Composite Layers with Ceramic Matrix Modified with Glassy Carbon Destined for Oil-Less Sliding Pairings The paper presents basic knowledge about producing and some results of tribological and metallographical research on composite layers with porous, anodic hard coating matrix which were modified with glassy carbon nanotubes. These composite layers were formed as surface layers of machine parts operating under conditions of sparse lubrication (limited lubrication) and friction in air. The layers were tested at sliding mating with EN-GJL-350 cast iron used for piston rings in combustion engines and air compressors. On the basis of the metallographical tests was the structure of the composite layer described. It was fount that on the surface of the oxide is a glassy carbon layer and in the pores of oxide are regullary carbon nanotubes. On the basis of the obtained results of tribological tests it was found that glassy carbon layer on the oxide surface shorts the wering-in time, and the glassy carbon nanotubes formed inside the pores of anodic hard coating upon EN-AW-6061 aluminum alloy prove to be effective solid lubricants and complement lubrication function of the graphite in cast iron. Consequently the coefficient of friction was lower than in case of nanotubes-free oxide layers.

Inheritance and the residual stress in the surface layer of machine parts

A method is proposed for calculating the residual stress in the surface layer of ground corrosion-resistant steel parts.

Depth of the shot-hardened surface layer on machine parts

The contact interaction in the shot hardening of the surface layer of machine parts is investigated. A formula is obtained for the depth of the shot-hardened layer as a function of the machining conditions and the mechanical properties of the material.

Electrospark Deposition by Using Powder Materials

Electrical discharges can be used to improve the operational properties of the surface layer of parts by using the phenomena of tempering, alloying, and deposition. Various techniques of alloying or deposition have been studied so far and sometimes even applied in the industry. The systemic approach of the deposition process shows which input and output factors can be taken into consideration. This article presents the experimental results obtained by using the deposition process based on the introduction of additional material such as powders put directly in the plasma channel corresponding to the electrical discharge. The established empirical mathematical models emphasize the influence exerted by the work gap value between the electrode and the workpiece, the powder flow, the delivered energy, and the specific energy on the quantity of added material.

Principles for determining the deformed state of the surface layer and precision of machine parts in cutting

645 The existing theory of cutting and the specification of the cutting conditions corresponding to the required surfacelayer properties and precision rely on experimental data and mathematical models obtained by regression analysis. Consequently, the results can� not be extrapolated to an expanded range of cutting parameters. Accordingly, there is a need for additional experiments to improve the existing mathematical models, especially as the shaping kinematics become ever more complex in the machining of metals. In modern equipment, shaping is undertaken by multi� coordinate machine tools equipped with a cutting tool of complex geometry, with sharp increase in the fluc� tuation of the margin and corresponding decrease in precision of the calculations. Physically, the operational properties in the surface layer depend on two basic factors: (1) cold working by residual compressive stress, with increase in wear resis� tance of the surface layer as machining continues; (2) heating of the surface layer as a result of plastic deformation, with partial tempering of the surface layer and the formation of tensile stress. As yet, there has been no reliable analytical calculation of the resid� ual compressive stress, and hence reliable prediction of the time required for runningin of the surfaces is impossible. Such analytical solutions would permit sharp reduction in the time for runningin of the sur� faces and thereby extend the period of steady wear. They would also significantly reduce the costs of pre� paring plant standards and permit improvement in the

Analysing the Properties of Surface Layers Generated by Sheet Metal Forming Operations

The paper brings results of the surface layers properties analysis of a thin wall hollow sheet metal parts, produced by metal spinning and deep drawing. The influence of mandrel (workpiece) frequency of rotation on the spun parts surface layer strainhardening is studied and compared with the quality of the formed part surface layer produced by deep drawing technology.

Plasma-Detonation Technology for Modification of the Surface Layer of Metal Parts

Structuring of surfaces of metal parts is performed with the electric current commutated by the pulsed plasma. Alloying elements are added to plasma and participate in a micro metallurgical process occurring on the molten surface of a part. Heat capacity of metal of the part provides the high rates of cooling and solidification of the melt. Cycling of the melting and solidification process under conditions of pulsed physical fields provides stirring and crystallisation of alloy to form microcrystalline structures. The technology is implemented using ingenious accelerators of alloying elements, which are based on development of the non-stationary processes of detonation of combustible gas mixtures in the electric field. The surface is treated with the pulsed, electric, magnetic, acoustic and elastic-deformation fields, thus enhancing the abnormal heat and mass transfer processes and providing formation of new materials and alloys with microcrystalline structures in surface layer.

Development of a Wear Map for the Sliding and Rotational Wear behavior of Shafts

This study was an attempt to study the wear calculation method for rotating shaft in the friction couple type in conditions of oiling in high dusty environment. The size and quantity of abrasive particles that go into the clearance between friction surfaces, definition of the pressure including the load in conjugate that is given by the cuff spring as the radial force, and the effected contact area including the micro hardness of the shaft surface (taking into account the influence of the finishing treatment as a diamond pressing) have been calculated by utilization of above mentioned method. Furthermore, the volume wear has been calculated by the energy of friction including both the factor of energy transition to heat and the latent melting heat of shaft material. In this study the experimental scheme for wear testing of steel shaft in the friction couple type shaft-cuff and the theoretical and experimental results have been given, Fig. 4. It has proved that this method permits to choose the effective materials for parts making and the use of effective finishing treatment. Morethan, it permits to choose optimum properties of the parts surface layer. This may be attained on the stage of designing- to prognosis shaft and couple friction conjugates wear. Therefore, this method provides a maximum wear resistance and the ability to calculate parts life before damage.

Plasma impulse based peening and decoating of engine parts and pulsed plasma thrusters for small spacecraft propulsion

In a new line of research at the Institut für Raumfahrtsysteme (IRS), short-pulsed coaxial plasma accelerators for both industrial applications and space propulsion are being developed and experimentally investigated. First efforts led to the design of a plasma gun capable of delivering power densities of up to 2 GW/ cm 2 onto the surface of a thin-walled engine part subjected to high dynamic loads and, hence, prone to fatigue-induced failure. A short-duration high-power flux explosively evaporates a sacrificial coating and, thus, creates residual compressive stresses in the part's surface layer, improving its resistance against fatigue. The plasma accelerator is presently being assembled and will be operational soon. In a continuation of this work, this device will be reversibly modified to also allow for the plasma impulse based removal of partially eroded coatings for thermal, corrosion and abrasion protection from aeronautical engine parts during their regular maintenance. In parallel and based on the same short-pulsed plasma gun technology IRS also investigates pulsed plasma thrusters for primary and secondary propulsion of small satellites and spacecrafts, hence, making maximum use of the synergies. The theoretical design of the different plasma accelerators and their technical realization will be presented.

Termomechanical processing of titanium alloys by high power pulsed ion beams

The effect of thermomechanical processing by high power pulsed ion beams (ions of C +and H +, energy, E=300 keV, ion current density in a pulse, j=20–220 A·cm −2, number of pulses, n=1–100, pulse duration, τ=50–100 ns) on the chemical composition and structure of titanium alloy parts surface layers (VT8M, VT9, VT18U and VT25U) were studied. It is shown that ion beam treatment and a post-process annealing allow the modification of the surface layers of the titanium alloy parts with thicknesses up to 100 μm. As a result of this complex treatment, service properties of the titanium alloy details can be improved cardinally. The prospects of high power pulsed ion beam treatment application for aircraft engine building are discussed.

Computational determination of the structure and hardness of rolls after induction hardening

The main problem of induction hardening consists in obtaining the requisite hardness of the surface layers of parts. In hardening rolls by currents of commercial frequency the hardness and thickness of the hardened layer are determined by the speed of motion of the inductor, its power, and the intensity of the sprayer cooling. The choice of these parameters with the help of a full-scale experiment is a very expensive and laborious operation. For this reason it is expedient to determine the regimes of induction hardening with the use of numerical experiments. The present work is devoted to the creation of software for computing the hardness in induction hardening from the cross section of the roll. Since the hardness of the steel is determined primarily by the structural state that dependes on the temperature regime, the software should included the solution of problems of thermal conduction, determination of the structural state, and calculation of the hardness as such.

Structure and properties of gray cast iron after electromechanical machining

1. Electromechanical machining (EMM) of parts made of gray cast iron yielded a strengthened layer with good operating properties: wear resistance, heat resistance, and corrosion resistance. 2. The strengthening of the surface layer of parts made of gray cast iron SCh21 in EMM is connected with its hardening and the formation of a large amount of residual austenite. 3. It is recommended to apply EMM to parts operating at high temperatures and under large loads (cylinders, piston rings of internal combustion engines).

A calculation investigation of the influence of stresses on the structure of steel parts being hardened

1. According to the data of a calculation analysis internal stresses may both accelerate and slow formation of pearlite and bainite in steel parts and, in particular, cause reverse hardening in quenching. 2. Stresses have a stronger influence on the degree of development of the pearlitic transformation in the axial zone of rotor-type parts than on the hardenability of the surface layer of rolling roll-type parts. 3. With a sufficiently high sensitivity of transformations in steel to stresses there is a cooling rate of parts in quenching, exceeding of which is undesirable, which is the optimum for suppression of the pearlitic transformation in the axial zone. 4. The structure of the axial zone of parts may be improved by the use of stepped hardening cycles with slowed cooling during the martensitic transformation in the surface zone of the metal.

Investigation of the processes of recrystallization in the surface layer of brass parts after cold deformation and annealing

Investigation of the processes of recrystallization in the surface layer of brass parts after cold deformation and annealing

Trenie Iznos : G. I. Kozlov, L. N. Obischenko, N. M. Mikhin, D. A. Dergobuzov, A. D. Sokurenko and Yu. A. Deikina, studies of the effect of laser hardening under conditions of deep melting on physical-mechanical properties of the surface layers of steel parts and their abrasive wear resistance, 5 (2) (1984) 251

A wood-polymer composite has been produced by impregnating the wood with the monomer and subsequently polymerizing it by exposure to a gamma radiation source. To compare the improvement in creep deformation of the wood due to the polymer impregnation, a nonlinear Norton-Bailey isothermal mathematical function has been used to model the bending creep deformation of the wood-polymer composites. Results show that the impregnation significantly improves the creep resistance of the wood. The maximum creep resistance is obtained when the amount of polymer impregnation exceeds about 30%. An interfacial interaction between the wood cell wall and the polymer could explain the creep deformation improvement, as well as the maximum impregnation level beyond which little improvement occurs. The results indicate that polymer impregnation is a viable method for improving the poor creep properties of wood.

Thermally stressed condition occurring in the surface layers of flat parts during friction hardening

Thermally stressed condition occurring in the surface layers of flat parts during friction hardening

Complex diffusion alloying of sintered materials

1. A mixture whose alloy component is of 180- to 315-μ particle size possesses optimum alloying properties. Use of such a mixture enables the mechanical characteristics of parts from sintered materials to be improved by 15–20%. 2. The addition of 1.5–2.0% of carbon to a starting material reduces the diffusional mobility of impregnating elements in the surface layers of parts, as a result of which coherent, nonporous layers are formed composed of Me23C6 and Me7C3 carbides. 3. Diffusion alloying with a group of elements substantially increases the strength and oxidation and corrosion resistance of sintered materials.