Measurement of Residual Stresses in Electrochemically Metallized Coatings on Thin Cross-Cut Ring Substrate

Reitsnik

et al. 2014

AMR

Self Cite

Abstract. The investigated brush-plated gold and silver coatings are used for refining the surface properties of electric apparatuses. Tensile residual stresses generated in the plated coatings were determined by the curvature method and by instrumented indentation testing of a thin-walled open ring substrate, as described in our earlier papers. These stresses relax over time and their dependence on relaxation time was approximated by a linear-fractional function. The Young´s modulus and nanohardness of the coatings were determined. The surface morphology and structure in cross section of the coated substrates were presented. IntroductionHard gold and silver coatings have met application in engineering use (e.g. on generators slip rings, sliding contacts and small machine parts) due to their high hardness and wear resistance as well as their effective protection. They are typically plated on copper (mostly), brass and bronze. Silver is often used as low-price replacement for gold.Brush-plating is a simple processing method for selective plating of desired materials onto metallic materials without dipping the machine part (work piece) into a tank of the electrolyte. As the plating process takes place at room temperature, no heater is required. Usually, alloying metals or nanoparticle composites are added to pure gold and silver. Nickel-hardened gold and silver coatings were brush-plated from an industrial SIFCO Dalic Solution (Gold Hard Alloy) pH 8.4, Code SPS 5370, and Silver Hard Heavy Build pH 11.7, Code SPS 3083, on thin-walled open copper and brass ring substrates of various thickness [1,2,3]. In the present paper residual stresses in the plated coatings were determined by the curvature method and by an instrumented indentation testing technique. Relaxation of residual stresses was observed over a long time and some properties of the coatings, e.g. modulus of elasticity and nanohardness, which affect the service life of electrical components, were determined.

Section: Residual Stresses In the Coatings And Experimental Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Relaxation of Residual Stresses in Brush-Plated Gold and Silver Coatings on Copper and on Brass Substrates

Reitsnik

et al. 2014

AMR

Self Cite

“…The strips (section dimensions 22×0.955 mm, total length 70 mm, coated length 51 mm) used as the substrate were cut from a rolled brass ribbon (E 1 = 99.1 GPa, µ 1 = 0.34 (62-65)%Cu [9]). After cleaning and polishing both surfaces, the thickness of the substrate was measured with an accuracy of 0.01 mm and a temperature compensated strain gauge (KF5P1-15-100-B-12, basic length 20 mm, resistance 100 Ω, gauge factor 2.2 at (20±1)ºC, Co VEDA, Kiev, Ukraine) was glued onto the back surface of the strip as shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…The substrate was electrocleaned by forward polarity with a voltage of 10 V for about 0.5 minutes (cleaning solution Code SCM 4100, sodium hydroxide (3-4) %) and rinsed. A nickel coating (E 2 = 163 GPa, µ 2 = 0.324, [9]) was deposited from the electrolyte elaborated by M. Pille, PhD (Estonian University of Life Sciences), containing NiSO 4 ×7H 2 O, 350 g/litre; HCOOH, 60 g/litre; HCOONa×2H 2 O, 40 g/litre; MgSO 4 ×7H 2 O, 10 g/litre; gravity (1.19±0.01) g/cm 3 , pH = 1.57-1.63 (determined at 20ºC). The stylus was swabbed over the area where the coating was to be deposited, using a current density of (60-64) A/dm 2 Fig.…”

Section: Methodsmentioning

confidence: 99%

S57 Residual Stresses Analysis in Brush-Plated Galvanic Coatings Deposited From Nickel Sulfate Electrolyte

2008

Powder Diffr.

Residual stresses are investigated in brush plated hard coatings deposited from nickel sulfate electrolyte. To determine residual stresses, a conventional deformation method was used, where a coating is manually deposited on a brass strip substrate in the conditions of restraint bending. The change in the axial strain of the free surface is measured by strain gauges after releasing the substrate from the fixture. The dependence of deformation on coating thickness is used as experimental information. The sensitivity of the method is studied and the expanded uncertainties of the computed mean values of residual stresses are presented. Residual stresses are also determined by the X-ray diffraction technique, based on the sin 2 ψ method. Residual stresses in the surface layer of coatings represent tensile stresses and their maximum value is (755±106) N/mm 2 and (760±250) N/mm 2 , obtained by the deformation method and by the Xray diffraction technique, respectively; the other values at different coatings thicknesses are comparable within the maximum limit of measurement uncertainty.

“…Calculation shows that higher deposition temperature causes temperature stresses whose role in residual stresses is not significant [5].…”

Section: Evaluation Of Residual Stresses In the Coatingmentioning

confidence: 97%

Determination of Modulus of Elasticity, Nanohardness and Residual Stresses in Brush-plated Gold and Silver Coatings on Copper Substrate

Veinthal

et al. 2012

In the current study the investigated brush-plated gold coatings are generally used for repairing the commutators of generators and sliding contacts made in most cases of copper. Considering the cost, gold is sometimes replaced by silver in manufacturing electronic components.

Nickel-hardened gold and silver coatings were brush plated from a commercial SIFCO Dalic Solution (Gold Hard Alloy), Code SPS 5370, and Silver Hard Heavy Build, Code SPS 3080, on unclosed thin-walled copper ring substrates.

The magnitudes of the modulus of elasticity and of nanohardness of the coatings were obtained by instrumented indentation using the MTS Nano Indenter XR^® and the Micromaterials Nano Test system pendulum-type nanohardness tester. Residual stresses in the coatings were calculated from the curvature changes of the substrates and they represented tensile stresses. Relaxation of residual stresses was observed. An equation for approximation of the change of residual stresses was applied assuming that the dependence of residual stresses on relaxation time is linear-fractional. The values of residual stresses in the gold and silver coatings decreased considerably, during the first weeks in particular. The equation for approximation of the change of residual stresses allows to predict the finishing residual stresses in the coating for the exploitation period within the limits of measurement uncertainty.

The surface morphology and microstructure of the coatings was studied by means of scanning electron microscopy (SEM).

DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1341