In order to investigate the effect of nitriding conditions on the hardness and thickness of the nitrided layer in nickel alloys, a tentative nickel binary alloy of Ni-30wt%Cr was nitrided in plasma nitriding at different nitriding temperatures ranging from 673 to 1073K nitriding times of 3.6 to 32.4ks, nitrogen gas concentrations in N2+H2 mixed gas of 10 to 100vol%, gas pressures of 270 to 1330Pa, discharge voltages of 270 to 420V and current densities of 14.2 to 19.5A/m2. Nitriding temperature was the parameter that affected the hardness of the nitrided layer. The maximum surface hardness was Hv 760 at a nitriding temperature of 823K. The thickness of the nitrided layer depended on the nitriding temperature, nitriding time, and nitrogen gas concentration. Gas pressure, discharge voltage, and discharge current density, however, did not affect surface hardening in the nickel alloy. In this study, we determined that the optimum nitriding conditions for surface hardening of nickel alloys by plasma nitriding were temperature at 823K and 90vol%N2+ 10vol%H2 mixed gas atmosphere at 800Pa.
A new method has been developed to diffuse aluminum onto austenite stainless steel sheet. In the present study, samples diffused Al onto SUS 310S stainless steel were made by changing the thickness of Al foil attached on the surface of SUS 310S and varying heat treatment conditions. The structural changes in the diffusion layer and the mechanical properties of the samples were then investigated. The diffusion layer consisted of two layers: Layer I was α2 (FeAl) and layer II was a mixed structure of NiAl and α. Kirkendall voids were observed between the two layers. The hardness of layer I increased with increasing Al concentration, which was consistent with that of Fe-Al intermetallic compounds reported by others. That of layer II and the substrate was hardly changed by the aluminized coating. Tensile properties were strongly affected by surface cracks occurring on the diffusion layer during loading. The number of serrations appeared after yielding on the stress-strain curve correlated to that of cracks. The yield strength of layer I was evaluated by rule of mixtures, in which the yield strength had a peak in the vicinity of an Al concentration of 20wt% because of the strengthening mechanism brought about by mixing ordered and disordered phases. The tensile strength and elongation of samples decreased with increasing the thickness of the diffused layer and decreasing Al concentration due to the effect of three-axis stress under the crack tip.
In a study of the effect of 2-2'-bipyrizyl (bipy) and potassium ferrocyanide (ferro) on the plating of copper in Cu-triethanolamine (TEA) solution, we found that in a bath of high Cu concentration (0.06M) with a low TEA/Cu ratio (=7/6) (Bath A), bipy accelerated the oxidation of formaldehyde cooperating with the Cu-TEA complex, which resulted in a high plating rate but in poor adherence and smoothness. In a bath of a lower Cu concentration (0.03M) with higher TEA/Cu ratio (=5) (Bath B), bipy showed a fine leveling effect with diminuation of the accelerating effect. These effects were explained by a competitive adsorption model. Bath B was more stable than bath A, and this characteristic was markedly enhanced by the addition of ferro of 300ppm. A smooth adhering film was obtained from bath B containing 20ppm bipy and 300ppm ferro at 60°C under a stirring condition at a rate of 15μm/h.
Fine gold lines were deposited from a flowing plating solution. Plating experiments were conducted under potentiostatic conditions with an argon ion laser focused on a nickel-plated copper-zinc cathode substrate. All deposits were examined using a scanning electron microscope and a profilometer. The effects of the laser scan rate, laser power, and the cathode potential on the properties of deposits, the deposition rate, and pattern size were studied. Laser-plated lines have a dense structure, good adhesion to the substrate, and a low electrical resistivity of 5-15× 10-6Ωcm. Scanning of the laser beam enhances charge transfer, resulting in deposition rates as high as 30μm/s and line writing speeds as high as several hundreds of μm/s for incident laser power levels of 3W. Line widths increase exponentially with increasing cathode potential and increase linearly with increasing laser power.
When zinc ions are added in noncyanide silver electroplating, temperature obviously affects the surface appearance, structure, and the amount of zinc electrodeposited, while the effects of pH and additives were less. Adding sodium thiosulfate makes the grain size of electrodeposits fine, causing a low Miller index plane and orientation toward the (111) plane. Under the condition of a high sodium thiosulfate concentration, the orientation is especially strong. Also, in higher-current-density silver-zinc alloying, the orientation is changed toward (111) of the Ag-Zn alloy with an increase in zinc ions. At a limiting current density, zinc content is comparatively enlarged. At higher concentrations of zinc ions in the solution, the zinc content in the deposited film increases.
The morphology of the Sn-Sb alloys electrodeposited from 1-hydroxyethane-1, 1-diphosphonic acid solutions has been studied by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Increasing the Sb content of alloys tends to make the surface morphology fine and amorphous. A cross-section of the electrodeposited Sn-27wt%Sb alloy revealed a network structure based on a Sn-37wt%Sb alloy phase and β-Sn phase. The Sn-40wt%Sb alloy was found to consist of homogeneous microcrystals, while the Sn-63wt%Sb alloy consisted of two phases of a SnSb intermetallic compound (60wt%Sb) and an amorphous structure (82wt%Sb). The results of XRD and EDX analyses showed that as-plated Sn-Sb alloys were a single β-Sn phase at a Sb content of 3-7wt%, β-Sn+SnSb phases at 10-36wt%, a single SnSb phase at 40-60wt%, and SnSb+amorphous phases at 60-75wt%. As-plated alloys containing 75-85wt%Sb had an amorphous structure, and alloys annealed at above 160°C showed the presence of SnSb+Sb phases.