Comparison of advanced techniques for mechanical surface treatment of stainless steel parts

This work compares various mechanical surface treatment techniques applied to improve the properties of the AISI 304 austenitic stainless steel. Effects of laser shock peening (LSP), water jet cavitation peening (WjCP), water jet shot peening (WjSP), and ultrasonic impact treatment (UIT) on surface roughness, hardness, and residual stress were studied. The results demonstrate that as compared to the untreated specimen (Ra = 3.06 μm), all strain hardening methods demonstrate the decreased surface roughness parameters. The smallest Ra parameter of the wavy regular surface microrelief is formed after the ultrasonic treatment. The surface hardness (22.1 HRC5) was respectively increased by 30.7%, 38.4%, 69.6%, and 73.2% after the LSP, WjCP, WjSP, and UIT treatments. All peening techniques induced compressive residual stresses (ranged from –377 MPa to –693 MPa) in the near-surface layer. It is assumed that used treatments can increase wear/corrosion resistance and fatigue life in the studied steel.

Pulsed Mechanical Surface Treatment—An Approach to Combine the Advantages of Shot Peening, Deep Rolling, and Machine Hammer Peening

Several manufacturing processes are used to beneficially influence the surface and subsurface properties of manufactured parts. Different aspects such as the surface topography or resulting residual stresses are addressed using different manufacturing processes. This paper presents the first approach for pulsed mechanical surface treatment (PMST), a new manufacturing process aiming to combine the mechanics used in deep rolling and shot or hammer peening. The process can generate a defined surface topography while constantly impinging a mechanical impact on the workpiece. Two different tools (type 1 and type 2) have been designed to approach this new concept. Hardened carbide pins are used for type 1 to prove the concept using a simpler kinematic and resulting in a burnishing-like process. For type 2, hardened roller is used and results in an actual rolling process. Specimens made of S235 are processed in experiments with tool type 1 with varying pulse frequency and feeds. The resulting surface topography is described using optical measurement systems while micro-hardness measurements are used to describe the subsurface properties. The results in general show an increase of hardness in the surface and subsurface layer while the resulting surface topography can be directly controlled by the process parameters and therefore be designed for specific functional properties.

Laser Cavitation Peening and Its Application for Improving the Fatigue Strength of Welded Parts

During conventional submerged laser peening, the impact force induced by laser ablation is used to produce local plastic deformation pits to enhance metallic material properties, such as fatigue performance. However, a bubble, which behaves like a cavitation, is generated after laser ablation, known as “laser cavitation.” On the contrary, in conventional cavitation peening, cavitation is generated by injecting a high-speed water jet into the water, and the impacts of cavitation collapses are utilized for mechanical surface treatment. In the present paper, a mechanical surface treatment mechanism using laser cavitation impact, i.e., “laser cavitation peening,” was investigated, and an improvement in fatigue strength from laser cavitation peening was demonstrated. The impact forces induced by laser ablation and laser cavitation collapse were evaluated with a polyvinylidene fluoride (PVDF) sensor and a submerged shockwave sensor, and the diameter of the laser cavitation was measured by observing a high-speed video taken with a camera. It was revealed that the impact of laser cavitation collapse was larger than that of laser ablation, and the peening effect was closely related to the volume of laser cavitation. Laser cavitation peening improved the fatigue strength of stainless-steel welds.

Effect of Mechanical Surface Treatment on the Bonding Mechanism and Properties of Cold-Rolled Cu/Al Clad Plate

In the case of valuable cold-rolled Cu/Al clad plates, billet surface treatment before rolling is a significant process that can affect the bonding efficiency and quality. While the current studies primarily focus on the influence of rolling parameters, insufficient attention has been paid to surface treatment. In this study, the effects of mechanical surface treatment on the bonding mechanism and bonding properties of cold-rolled Cu/Al clad plates were investigated. The results showed that different mechanical surface treatments have significant effects on the surface morphology, roughness, and residual stress. In addition, the effect of surface mechanical treatment on bonding quality was also observed to be critical. When the grinding direction was consistent with the rolling direction (RD), the bonding quality of the Cu/Al clad plates was significantly improved. After surface treatment along the RD for 20 s, the Cu/Al clad plates showed the highest shear strength (78 MPa), approximately four times as high as that of the unpolished samples. Simultaneously, the peel strength of this process was also significantly higher than that achieved via the other processes. Finally, on the basis of the surface morphology, roughness, and residual stress, the effect of surface treatment on the bonding mechanism and bonding properties of Cu/Al clad plates was analyzed. This study proposes a deeper understanding of the bonding behavior and bonding mechanism for cold rolled clad plates processed via mechanical surface treatment.

Effect of Various Surface Treatments on Ti-Base Coping Retention

Clinical Relevance Mechanical surface roughening of the titanium-abutment base is necessary to increase the pull-off bond strength of the lithium disilicate abutment material. Additional chemical surface treatment may further increase the bond strength, but the effects are product specific. SUMMARY Objective: The titanium-cement interface of a Ti-Base implant crown must be able to resist intraoral pull-off forces. The purpose of this study was to evaluate the effect of mechanical and chemical surface treatments of a titanium-abutment base (Ti-Base, Dentsply/Sirona) on the pull-off bond strength of a lithium disilicate abutment coping. Methods and Materials: Ti-Bases were divided into nine groups of 10 copings each that varied in both mechanical surface treatment (none; Al2O3 air abrasion; CoJet silicoating, 3M ESPE) and chemical treatments (none; Monobond Plus, Ivoclar Vivadent; Alloy Primer, Kuraray). Lithium disilicate abutment copings (IPS e.max CAD, Ivoclar Vivadent) were designed and milled. After crystallization, the copings were cemented onto the Ti-Bases with a resin cement (MultiLink Hybrid-Abutment Cement, Ivoclar Vivadent) according to the manufacturer's recommendations. The copings were torqued to a mounted implant, and the access channel was sealed with composite. After 24-hour storage and 2000 thermal-cycles in distilled water, the copings were subjected to a removal force parallel to the long axis of the interface until fracture. Data were analyzed with multiple one-way analyses of variance and Tukey post hoc tests (α=0.05). Results: Significant differences were found between groups based on type of surface treatment (p<0.05). Conclusions: Chemical surface treatment with Monobond Plus and mechanical surface treatment with CoJet silicoating or Al2O3 air abrasion resulted in the greatest pull-off bond strength. Alloy Primer did not provide a statistically significant increased pull-off bond strength when the surfaces were mechanically treated with Al2O3 air abrasion or CoJet silicoating. The lack of any mechanical surface treatment resulted in the lowest pull-off bond strength regardless of the type of chemical surface treatment.

Komplementärzerspanung – Zerspanung und mechanische Oberflächenbehandlung in einer Aufspannung/Complementary Machining – machining and mechanical surface treatment in one clamping

Bei der Herstellung hochbelasteter Bauteile folgt nach der Zerspanung oftmals eine mechanische Oberflächenbehandlung, um Randschichtzustände, wie Rauheit oder Verfestigung gezielt einzustellen. Bei der Komplementärzerspanung erfolgt die Zerspanung und mechanische Oberflächenbehandlung in einer Aufspannung mithilfe des Werkzeuges. Nachfolgend wird das Potenzial der Komplementärzerspanung bei der Bearbeitung des Stahls 42CrMo4 und der Aluminiumlegierung AlCuMgPb hinsichtlich der Rauheit aufgezeigt. In the manufacturing of highly stressed components, machining is often succeeded by a mechanical surface treatment in order to specifically modify surface layer conditions such as roughness or hardening. In the process of Complementary Machining, machining and mechanical surface treatment are performed in one clamping with the use of the tool. In the following, the potential of Complementary Machining when treating steel 42CrMo4 and aluminum alloy AlCuMgPb with regard to roughness is shown.