Investigation of slurry erosion wear behavior of steel materials used in seawaters

Slurry erosion is a wear process that results from the interaction of the liquid with solid particles suspended in it and the surface of the material, causing severe damage to the materials. In this erosion process, massive loss occurs as a result of repeated contact of the particles to the material surface. Propellers, valves, turbine blades, sludge pumps and solid particle carrying pipelines are industrial application equipment where slurry erosion is often encountered. Slurry is not yet fully understood because it is a complex process affected by many factors such as erosion flow field parameters, target material properties and abrasive particle characteristics. Among these factors, the impact angle and the microstructure of the target material play the most important role on the material removal process. In the literature, researches have been continuing thoroughly together with the studies on slurry erosion behaviors of ductile and crunchy materials and parameters affecting slurry erosion. Because three sides of our country are surrounded by four seas and there are sea links with many countries, more than half of both exports and imports of Turkiye's foreign trade are carried by sea transport. Turkiye is also home to very important ports at the intersection of the east-west and north-south international transport corridors with the ports at strategic locations in the maritime lines, therefore we have foreign flagship commercial, tourist and transit fleets in our sea waters. In addition to all these, the Turkish Naval Forces are also of great importance in terms of defense and security. This study provides an examination of slurry erosion at different sea water concentrations (especially seawaters in Turkey). In this thesis, the effects of experimental parameters, angle of attack, slurry velocity, sand particle size and sand concentration on slurry erosion in both of water-sand and saline-sand mixtures of steel sheets reference material were compared using a specially designed test setup. Within the scope of this postgraduate thesis, when examining the slurry erosion wear in different sea water concentrations (different concentrations of the four seas on three sides of our country have been prioritized), the idea that sample, abrasive (particle properties and size, impact angle, velocity) and test time combinations have been examined with a single experimental setup has been established. Therefore, in this study, with materializing a slurry erosion tank test device design, it was aimed to make an important contribution to increase the service life of materials exposed to slurry wear in machinery and parts working in an aqueous environment, around bridges in marine / dam / river area in ship propellers. Thus, if behaviors against slurry erosion wear are known, the most appropriate and economical methods of protection are questioned for systems and parts exposed to this erosion. In the present work, erosion wear due to water–sand/saline-sand mixture have been investigated using a slurry erosion pot tester. In the experimental study, slurry erosion wear behavior of St 12 / A366/CQ quality dekape steel sheet material was investigated in water-sand slurry and saline-sand slurry respectively. For slurry; 400 μm Al2O3 Al2O3 and steel grid abrasive particles and brine from the Mediterranean, Black Sea and Aegean Sea were also used to compare with the mains water. Slurry erosion wear behaviors of the samples at 30⁰, 60⁰ and 90⁰ impact angles were examined by means of the sample holders connected to the revised bench top column drill. The experiments were carried out in three sets for 300 min at spindle rotation speed 1900 rpm. Corrosive particle size, concentration percentage, impact velocity parameters were kept constant and the results of the change in erosion rate caused by impact angle and salinity density were compared. Abrasive particle size, concentration percentage, impact velocity parameters were kept constant and the results of the change in erosion rate caused by impact angle and salinity density were determined. The results showed that slurry erosion wear increased as salinity increased. Maximum erosion wear was observed at 30⁰ in the Mediterranean saline-sand slurry, and minimum erosion wear was measured at 90⁰ in water-sand slurry.