The influence of dispersed phase on plasma spraying coatings MMC with alloy matrix Ni-Al properties
Robert Starosta
Quarterly No. 1, 2009 pages 89-93
DOI:
keywords: composite coatings, corrosion, plasma spraying
abstract The operating of machines and devices caused wear of their pieces. This wear is the result of corrosive, tribology and fatigue processes. The wear of units forces the periodic inspections and the dimension verification, sometimes the replace or the regeneration of injured elements. A lot of consequences of wear processes can be restrict by surface layer modifying or coating obtaining. The electrolytic chromium coutings or rarely surfacing by welding stellit and nimonics layer or chemical Ni-P coatings are often applied in building of machine. Coatings with diversified properties, which will be able to fulfil the operation requirements and to prolong the safe life of machine element, we can obtain by plasma spraying thermal process. The metallic alloy Ni-5%Al and composite Ni-5%Al-Al2O3 coatings were investigated. These coatings were obtained by plasma thermal spraying. The coatings were prepared on the carbon steel C45. The volumetric contents of aluminium oxide in composite coatings numbered 15, 30 and 45%. The thickness, roughness, microhardness and the corrosive proprieties of coatings were tested. The corrosion tests were performed by potentiodynamic method. The specimen of 1 cm2 surface was rinsed with acetone, and then put into the cell, in which the anode made of platinised titanium and reference saturated calomel electrode were also immersed in 0.01 M H2SO4 at ambient temperature. The solution was constantly stirred. The polarization curves were obtained at a 10 mV/min rate of potential shift, within the region from stationary potential after 0.5 hour of pre-exposure in the electrolyte. As the first the cathodic curve, and then anodic curve were recorded. The corrosion current was determined. Negative effects of presence of alumina particles on corrosion behaviour of such coatings have been observed.