The effect of pre-heat and post-heat treatment on the hardness and blackening process of electroless NiP deposits on titanium alloy

Abstract

The black coatings were fabricated via electroless NiP deposits on Ti-6Al-4V alloy substrate with heat-treatment and blackening process. Two types of coatings were obtained: coatings with heat-treatment after blackening and coatings with blackening after haet-treatment. After parameter optimization, the temperature and pH of the solution were adjusted to 85 °C–95 °C and 4.3–4.7, respectively. The substrate was coated after the addition of modifying components to the solution. After refluxing the samples, the blackening process was done for 40 s in nitric acid (9molar). An SEM-EDS analyze used to assess the morphology and chemical composition of the coating. Moreover, adhesion strength and optical absorptance of the coating were measured by Pull Of test and Shimadzu UV-3100 analysis, respectively. The optical absorptance was measured by 0.89 and 0.95, respectively, for Oxalic acid and Nitric/Flouridric acid pretreated samples. Results showed that heat-treatment after blackening causes coating with higher micro-hardness and optical absorption. The blackened electroless NiP coating on Ti substrate with the heat-treatment of 4 h after the blackening process provided high solar absorption of 0.99, which is exceptionally suitable as a solar absorber coating for space and allied applications.

Computer‐aided selective production of low-resistance NiP and NiCuP layers

“…To clearly and precisely determine the influence of nickel plating process parameters, all dependences are based on measurement data obtained by means of the following series of measurements: metallization speed VR as a function of temperature T of metallization bath for acidity range of pH = (1.0Ä3.5), other values are also found in the literature (Alhaji et al, 2020); however, with regard to resistive and conductive layers, it is not possible to use concentrations with a pH value higher than 3.5; The authors' experimental results obtained during many years of research were used to build all the relationships (1-6) on which the created mathematical model of the metallization process is based. The collected data concerning the relation between metallization speed V R [m m/h] and temperature T [K] was approximated with a quartic polynomial that best matches the distribution of experimental points of the process:…”