The effect of slide burnishing (SB) on the high‐cycle fatigue (HCF) performance of 2024‐T3 high‐strength aluminium alloy has been studied. After SB with optimum basic process parameters under ‘minimum roughness’ criterion, the 107 cycle fatigue strength increases with 25% – from 180 to 225 MPa, fatigue life is increased more than 50 times, and the roughness obtained reaches up to Ra = 0.05 μm. Further, various combinations of burnishing force and deforming element radius have been applied to reach maximum HCF performance despite roughness obtained. It has been established that with the optimum combination under ‘maximum HCF performance’ criterion, 107 cycle fatigue strength increases with 44% – from 180 to  260 MPa as the roughness obtained is Ra = 0.25 μm. This significant enhancement in the HCF performance is due to introduced beneficial residual compressive stresses. They shift the fatigue crack initiation site from surface to subsurface layers and, as a result, the nucleation and propagation of the first‐mode fatigue cracks are retarded. In order to establish the fatigue limit (based on 2  ×  108 cycles), a combined approach, based on limited Wöhler's curve and Locati's method, has been applied. The fatigue limit of 2024‐T3 high‐strength aluminium alloy can be increased up to 250 MPa using SB with optimal basic parameters under ‘maximum HCF performance’ criterion.

Chromium-nickel steels are widely used in various fields of the engineering practice because of their increased corrosion resistance. One of the most used chromium-nickel steel is AISI 316Ti. It is known from the engineering practice that processing this steel by cutting creates difficulties and problems. However, there is no information regarding the effectiveness of the slide burnishing (SB) method in terms of quality of the processed surface of this chromium-nickel steel. A comprehensive experimental and FEM study of the surface integrity of slide burnished specimens made of AISI 316Ti austenitic stainless steel has been carried out. The effect of the SB parameters on the obtained roughness, microhardness, residual stress, fatigue strength (life) and wear resistance has been studied. A fully coupled thermal-stress FEM analysis has been conducted to be appreciated the effect of the generated temperature in SB process on the residual stress formation. The SB of AISI 316Ti steel achieves: roughness of R a = 0.055 lm; micro-hardness increased by more than 32%; significant wear resistance; introduced residual stress with a maximum absolute value, which significantly exceeds the yield limit of the bulk material; increased fatigue strength by 38.9%; fatigue life increasing more than 385 times. The obtained experimental outcomes for the main characteristics of the surface integrity prove that SB can be successfully applied as a mixed burnishing for finishing symmetrical rotational components made of chromium-nickel steels.

No abstract

One of the methods for increasing fatigue life of symmetric rotary metal components is slide diamond burnishing (SDB). This method is implemented on conventional and computer numerical control machine tools by means of simple equipment, which is its main advantage. The SDB basic parameters are diamond insert radius, burnishing force, feed rate, and burnishing velocity. The additional ones are number of passes, working scheme, and lubrication conditions. The effect of SDB additional parameters on the fatigue behaviour of 2024‐T3 Al alloy was experimentally studied. Groups of smooth and notched hourglass‐shaped specimens were slide burnished using different combinations of additional SDB parameters and then were subjected to bending fatigue tests. The residual stresses, introduced by SDB, were measured by X‐ray diffraction technique. The near‐surface microstructure of the slide‐burnished specimens was investigated. Based on the results obtained, it was established that SDB produces two main effects, which depend on SDB additional parameters. The essence of the macroeffect is creation of residual compressive stresses in the superficial and subsurface layers. This stresses retard the formation and growth of fatigue macrocracks and thus increase the lifetime of slide‐burnished components. The microeffect is expressed in modifying the microstructure of the surface and subsurface layers, correspondingly, refining the grain and homogenizing and reducing the pores in the material. Such microstructure is characterized by increased plasticity and fatigue crack resistance. The fatigue life depends on the combination of these two effects. Thus, the desired fatigue behaviour of the slide‐burnished component can be ensured through an appropriate selection of the governing additional SDB parameters.

No abstract

Slide burnishing (SB) is a static mechanical surface treatment based on the severe plastic deformation of the surface for which the contact between the deforming element and the surface being treated is sliding friction. SB improves the surface integrity of metal structural and machine components dramatically. This paper is devoted to improving the fatigue strength of 41Cr4 steel hourglass-shaped specimens subjected to SB with a spherical-ended deforming diamond via different combinations of basic governing parameters. Since the residual compressive stresses introduced play a significant role for the fatigue behavior of the burnished components, a comprehensive parametric study of the SB process was conducted using fully coupled thermal-stress finite element (FE) simulations. The FE model's adequacy was proven via comparison of the FE results for the residual stresses with X-ray diffraction measurements. The results obtained show that the diamond radius and the burnishing force have the strongest effects on the residual stresses, which, in turn, have a significant influence on the fatigue strength, respectively, fatigue life. An extensive experimental investigation of the effect of the selected SB basic parameters on the fatigue limit of the slide burnished specimens was carried out using Locatti's method. The latter is based on the Palmgren-Miner linear damage hypothesis, which is a particular case of a general cumulative damage theory. A planned experiment was carried out, with the governing factors changed among four levels. Regression analysis of the experimental results was carried out, and a model for predicting the fatigue limit was obtained. Based on the model obtained, a one-purpose optimization was carried out using a genetic algorithm. By means of the optimal basic parameters, the fatigue limit of the processed specimens was increased by 22.7%-from 440 to 540 MPa. The fatigue life increased more than 100 times over after SB with the optimal basic parameters.

The surface cold working (SCW) of austenitic stainless steel (SS) causes martensitic transformation in the surface layers, and the percentage fraction of the strain-induced martensite depends on the degree of SCW. Higher content of α‘-martensite increases the surface micro-hardness and fatigue strength, but deterioration of the corrosion resistance is possible. Therefore, the desired operational behaviour of austenitic SS can be ensured by the corresponding degree of SCW and heat treatment. This article evaluates the effects of SCW performed by diamond burnishing (DB) and heat treatment on the surface integrity (SI), rotating fatigue strength, and corrosion resistance of AISI 304 austenitic SS for two initial states: as-received hot-rolled bar and initially heat-treated at 1100 °C for one hour followed by quenching in water. Then, DB was implemented as a smoothing and hardening process, both alone and in combination with heat treatment at 350 °C for three hours after DB. The electrochemical performance was examined by open circuit potential measurements, followed by potentiodynamic tests. For both initial states, smoothing DB provided the lowest roughness, whereas an improvement in the maximum surface micro-hardness was obtained after hardening DB and subsequent heat treatment. The maximum fatigue strength was obtained by hardening multi-pass DB without subsequent heat treatment for the as-received initial state. Smoothing DB and subsequent heat treatment maximised the surface corrosion resistance for the two initial states, whereas a minimum corrosion rate was obtained for the initially heat-treated state. For the as-received state, smoothing DB and subsequent heat treatment simultaneously lead to a high fatigue limit (equal to that obtained by hardening single-pass DB) and a low corrosion rate.

The slide burnishing process causes cyclic loading of the surface being treated, which provokes cyclic hardening. Using a forced‐controlled indentation test, the sixth “loading‐unloading” cycle was stabilised. The effect of the number of passes and the cyclic loading coefficient (CLC) on the fatigue performance of slide burnished specimens was investigated. Rotating bending fatigue tests were conducted using nine groups of hourglass shaped specimens, which were slide burnished through a different number of passes and CLC values. A stabilised cycle of the surface layer achieved with six passes, lead to largest fatigue limit, whereas the CLC exerted negligible influence on the fatigue performance. The observed phenomenon was explained through different residual stress relaxation rates, due to the rotating bending load, as well as with the obtained surface layer microstructure. The residual stress relaxation was investigated through rotating bending fatigue tests, using cylindrical fatigue specimens, followed by X‐ray stress analysis.