Abstract—Erosion and abrasion are wear mechanisms reducing the lifetime of machine elements like valves, pump and pipe systems. Both wear mechanisms are acting at the same time, causing a “Synergy” effect, which leads to a rapid damage of the surface. Different parameters are effective on erosive abrasive wear rate. In this study effect of particle impact angle on wear rate and wear mechanism of ductile and brittle materials was investigated. A new slurry pot was designed for experimental investigation. As abrasive particle, silica sand was used. Particle size was ranking between 200- 500 µm. All tests were carried out in a sand-water mixture of 20% concentration for four hours. Impact velocities of the particles were 4.76 m/s. As ductile material steel St 37 with Vickers Hardness Number (VHN) of 245 and quenched St 37 with 510 VHN was used as brittle material. After wear tests, morphology of the eroded surfaces were investigated for better understanding of the wear mechanisms acting at different impact angles by using Scanning Electron Microscope. The results indicated that wear rate of ductile material was higher than brittle material. Maximum wear rate was observed by ductile material at a particle impact angle of 30 0 and decreased further by an increase in attack angle. Maximum wear rate by brittle materials was by impact angle of 45 0 and decreased further up to 90 0 . Ploughing was the dominant wear mechanism by ductile material. Microcracks on the surface were detected by ductile materials, which are nucleation centers for crater formation. Number of craters decreased and depth of craters increased by ductile materials by attack angle higher than 30 0 . Deformation wear mechanism was observed by brittle materials. Number and depth of pits decreased by brittle materials by impact angles higher than 45 0 . At the end it is concluded that wear rate could not be directly related to impact angle of particles due to the different reaction of ductile and brittle materials. Keywords—Erosive wear, particle impact angle, silica sand, wear rate, ductile-brittle material. I. INTRODUCTION ROSION wear is the removal of the material from the target after many cycles of impacting particle to the surface in a particle-liquid medium. Erosion failure analysis was investigated first by Finnie [1], [2] and Bitter [3], [4]. Erosion wear has a dominant affect in pump, pipes, valves and sharp corners in the fluid transportation systems. To reduce the effect of wear, different methods are applied like; using suitable materials, new processing techniques and modified surface treatments and coatings [5], [6]. Many parameters are effective on erosive wear such as liquid type, solid particle E. Kosa is with Istanbul Technical University, Mechanical Engineering Faculty, 34437, Istanbul, Turkey (phone: 90-212-2931300 (2437); fax: 90- 212-2450795; e-mail: kose@itu.edu.tr). A. Göksenli is with Istanbul Technical University, Mechanical Engineering Faculty, 34437, Istanbul, Turkey (phone: 90-212-2931300 (2480); fax: 90- 212-2450795; e-mail: goksenli@itu.edu.tr). size and shape, amount of solid particles in the liquid, particle impact speed and attack angle, medium temperature [7]-[10]. Also material properties; hardness and toughness of material have a major role on wear of the material [11], [12]. To determine the effect of different parameters on erosion wear, several test methods are developed [13]-[15]. Effect of impact angle on wear rate and wear mechanism is very important. Different researchers have investigated the effect of impact angle on wear rate and wear methodology [16], [17]. Neilson et al. [18] developed an equation emphasizing the relation between wear rate and attack angle of the particle. Desale et al. [19] observed that maximum wear rate of a ductile material is between 15 0 -30 0 impact angle which decreases continuously with further increase of the attack angle up to 90 0 . Desale et al. [20] investigated aluminum (90 VHN) and stainless steel (210 VHN) and observed maximum wear rate at angle as 15 0 and 22.5 0 impact angles for aluminum and 304L steel, respectively. According to different scientists [21]-[23], maximum wear rate of ductile materials were observed by particle impact angles between 15 0 and 40 0 , while brittle materials such as glass, showed a maximum wear rate at 90 0 . According to [24], by the impact of particles normal to the target surface, deformation wear is produced and by particle velocity parallel with the surface is defined as cutting (microploughing) wear. Beside impact angle, material properties; hardness and toughness have also a strong effect on wear mechanism [23]-[25]. Unfortunately very limited studies were carried out to investigate effect of material hardness on erosion wear rate and mechanism. Oka [26] performed experiments to different materials to estimate wear rate by using sand blast type erosion test rig, by reaching velocities up to 130 m/s, but this impact velocities are not realistic values. Only maximum velocity of 20 m/s is reached in pumps or valves where erosion-corrosion is observed. Researches on the effect of both attack angle and hardness of metal materials on wear rate simultaneously has been investigated very limited [23]. Clark et al. [27] concluded that by increase of material hardness, not only wear rate increased, but also deformation wear rate increased with increase of impact angle by using test environment as diesel oil. But [27] used Pyrex glass as brittle test material and not hard metal, which is not a realistic approach because metallic materials are widely used in pumps and pipes. The aim of the presented research is to investigate the effect of impact angle and metallic material hardness on wear rate and mechanism. The investigated materials were non-heat treated and quenched St 37. Effect of Impact Angle on Erosive Abrasive Wear of Ductile and Brittle Materials Ergin Kosa, Ali Göksenli E World Academy of Science, Engineering and Technology International Journal of Mechanical and Mechatronics Engineering Vol:9, No:9, 2015 1638 International Scholarly and Scientific Research & Innovation 9(9) 2015 scholar.waset.org/1307-6892/10002428 International Science Index, Mechanical and Mechatronics Engineering Vol:9, No:9, 2015 waset.org/Publication/10002428