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Article
Publication date: 2 March 2015

Hamid Omidvar, Mohammad Sajjadnejad, Guy Stremsdoerfer, Yunny Meas and Ali Mozafari

This paper aims to coat ternary composite NiBP-graphite films by Dynamic Chemical Plating “DCP” technique with a growth rate of at least 5 μm/h, which makes this technique…

Abstract

Purpose

This paper aims to coat ternary composite NiBP-graphite films by Dynamic Chemical Plating “DCP” technique with a growth rate of at least 5 μm/h, which makes this technique a worthy candidate for production of composite films. Electroless nickel plating method can be used to deposit nickel–phosphorous and nickel–boron coatings on metals or plastic surface. However, restrictions such as toxicity, short lifetime of the plating-bath and limited plating rate have limited applications of conventional electroless processes.

Design/methodology/approach

DCP is an alternative for producing metallic deposits on non-conductive materials and can be considered as a modified electroless coating process. Using a double-nozzle gun, two different solutions containing the precursors are sprayed simultaneously and separately onto the surface. With this technique, NiBP-graphite films are fabricated and their corrosion and tribological properties are investigated.

Findings

With a film thickness of 2 μm, tribological analysis confirms that these coatings have favorable anti-friction and anti-wear properties. Corrosion resistance of NiBP-graphite composite films was investigated, and it was found that graphite incorporation significantly enhances corrosion resistance of NiBP films.

Originality/value

DCP is faster and simpler to perform compared to other electroless deposition techniques. Using a double-nozzle gun, metal salt solution and reducing agents are sprayed to the surface, forming a deposit. Previously, coatings such as Cu, Cu-graphite, Cu-PTFE, Ni-B-TiO2, Ni-P, Ni-B-P and Ni-B-Zn with favorable compactness and adherence by DCP were reported. In this paper, the authors report the application of the DCP technique for depositing NiBP-PTFE nanocomposite films.

Details

Anti-Corrosion Methods and Materials, vol. 62 no. 2
Type: Research Article
ISSN: 0003-5599

Keywords

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Article
Publication date: 9 October 2020

Ki-Woo Nam and Seo-Hyun Yun

The objective of this study was to perform damage analysis of SCM435 high-tension bolts connecting upper and lower parts of a three-stage injection molding machine.

Abstract

Purpose

The objective of this study was to perform damage analysis of SCM435 high-tension bolts connecting upper and lower parts of a three-stage injection molding machine.

Design/methodology/approach

Damage material used in this study was a SCM435 high-strength bolt connecting upper and lower molds of a three-stage injection mold. Causes of damage were determined by macroscopic observation. Microstructure observation was done using a metallic microscope, scanning electron microscope (SEM, S-2400, HiTachi, Japan), energy dispersive X-ray spectroscopy (EDS, Kevex Ltd., Sigma) and Vickers hardness tester (HV-114, Mitutoyo). Fatigue limit of the damaged material was evaluated using equivalent crack length.

Findings

Bolts were fractured by cyclic bending stress in the observation of ratchet marks and beach marks. The damaged specimen showed an acicular microstructure. Impurity was observed. Chromium carbide was observed near the crack origin. Both shape parameters of the Vickers hardness were similar. However, the scale parameter of the damaged specimen was about smaller than that of the as-received specimen. Much degradation occurred in the damaged specimen. Bolts should undergo accurate heat treatment to prevent the formation of chromium carbide. They must prevent the action of dynamic stresses. Bolts need accurate tightening and accuracy of heat treatment. Screws require compression residual stress due to peening.

Originality/value

This study conducted failure analysis of damaged SCM435 bolts connecting upper and lower parts of the three-stage injection mold. Fatigue limit of the damaged material was evaluated using equivalent crack length. In order to control this fracture, accurate tightening of bolts, accuracy of heat treatment and screws are required for compression residual stress due to peening.

Details

International Journal of Structural Integrity, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1757-9864

Keywords

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