A Study on Wear and Erosion-Corrosion Resistance of Two Typs of Cast Irons.


The wear and erosion-corrosion resistance of gray and ductile cast ironswere studied for their important in most applications. The wear tests were carriedout using a pin-on-disc machine by applying different loads (10,20 and 30 N). Thewear rate was measured using weighting loss method.Erosion-corrosion rate measurements for both types of cast iron in(0.01%,0.58% and3.5%) NaCl solutions using a rotating disc of 450 rpm indicatethat erosion-corrosion resistance of ductile iron is better than that of gray cast iron.Microstructure observations after erosion-corrosion indicate that it plays arole in erosion-corrosion ; the predominant ductile matrix on the microstructure ofductile iron is at lower erosion-corrosion rate than that of gray cast iron .Localized attack usually has bright surfaces free from corrosion product. Pits areoften observed on the line flow direction on these materials. These pits have acharacteristic horse shoes shape for both types of cast irons. Optical microscopeexamination for the specimens indicates the presence of white and dark areaswhich refer to graphitization and pitting corrosion respectively. The wear rate isinfluenced by the form of phases therefore the flake graphite form in gray actsmore like a lubricant film between two contact surfaces than spheriodalgraphite. Brinell hardness measurements for both materials show that gray iron hashigher hardness than ductile iron so that wear tests at different loads (10, 20 and 30N) for both materials indicate that gray iron has high wear resistance than ductileiron and the wear rate increases sharply after (20N) for ductile iron. These resultsare related to high hardness and graphite phase form on the microstructure of grayiron.