STUDIES ON EROSION WEAR BEHAVIOUR OF HIGH PURITY Ti AND Ta

Abstract

Erosive wear is caused by the impact of abrasive particles against a solid surface. Erosion is rapid and severe forms of wear and can results in significant costs if not adequately controlled. Erosive wear occurs in a wide variety of machineries and typical examples are the damage to gas turbine blades when an aircraft flies through dust clouds. The factors affecting the erosion rate are general factors and metallurgical factors. The general factors include• erodent particle hardness, size, shape, impact angle affect the erosion rate but these factor can't be changed. Only material characteristic/properties like material hardness, microstructure, toughness and strength could be changed to get better erosion resistance. This can be achieved through a heat treatment process. Hardness is the most important characteristic to consider while selecting the materials for minimum erosion rate. Generally wear resistance increases with hardness and decreases as toughness increases. But in the case of erosion, a combination of optimum hardness and toughness increases the erosion resistance. The basic aim of the present work is to study the effect of various heat treatments process on microstructure and on mechanical properties and the the influence of grain size variation on the erosion behavior of ductile materials, experiments were carried out on the body-centered cubic Tantalum, and the hexagonal close packed Titanium at impingement angle. The Ti samples were cold rolled and heat treated at different temperature for same time and Ta sample were heat treated at different temperature for 2h and 10h to obtain various grain size are used for mechanical tests . (Hardness test) and Air jet erosion test were conducted at various impact angle 300 to 90° and at room temperature. Microstructure changes were studied by using optical microscope. The effects of heat treatment on mechanical properties on erosion rate were studied with the help of suitable graphs. To study the material removal mechanisms, the Eroded surfaces of Ti and Ta impact samples were examined by scanning electron microscope (SEM) In the present study it was found that grain size of both Titanium and Tantalum increased with increasing heat treatment temperature and time. The hardness of Titanium decreased with increasing grain size but in the case of Tantalum hardness increased with iv increasing grain size. During erosion of investigated Titanium with alumina particle stream, it was found that the erosion rate increases generally with angle of impact and erosion wear resistance of finer grain size of is higher than other coarse grain size of Titanium. The mechanism of material removal is mainly due to ploughing and cutting. The entire work has been presented over six chapters in the dissertation. Chapter 1 presents the brief introduction about the project. Chapter 2 presents a review on erosion, mechanism of erosion, metallurgical factors affecting the erosion behaviour, Chapter 3 deals with the formulation of problem. Chapter 4 deals with the experimental study employed in the present study. Details of Air jet erosion test have been described. Details of various treatments given to Ti and Ta have been described. Details of instruments/machines and the techniques employed in the mechanical testing and metallographic study are given. Chapter 5 consists of characterization (micro structural and mechanical properties) and its changes with heat treated are given. The Air jet erosion resistance of the Titanium and Tantalum is also described. Chapter 6 presents the conclusions. V