Effect of the rigidity of the stress state on the wear resistance of materials in hydraulic and impact abrasion wear

Abstract

997.In the process of use many parts are subjected to the impact action of abrasive particles contained in a flow (jet) of gas or liquid and ones present on the contacting surfaces in the form of an abrasive layer. Despite the large number of publications devoted to problems of wear of parts, no universal criterion has been developed for evaluating the wear resistance of materials operating under various wear conditions. The present work concerns hydraulic and impact abrasion of various steels and alloys of nonferrous metals. In establishing the dependence of the wear resistance of the studied materials on their proper'des the authors take into account for the first time the rigidity of the stress state of the worn surfaces, which allows them to explain the special features of the behavior of the materials when subjected to various kinds of abrasion wear.In choosing the material for a part used under conditions of wear it is very important to determine what structure and properties are optimum for providing their maximum endurance [1,2]. The problem of optimizing the structure and properties to obtain a combination of high wear resistance and the requisite structural strength for the part, i.e., an optimum ratio of the surface and bulk strength of the part under specific operating conditions, is no less important. This paper presents results of a study of wear in various materials with the aim of developing a universal criterion of wear resistance.Tests of cylindrical specimens for hydraulic abrasion wear were conducted in a trough installation [2,3] with movement of the specimens at a linear sped v = 3.1 m/sec in a working medium consisting of water and quartz sand with particles 0.3 -1.6 turn in size in a 3-to-7 proportion (volume fractions).In tests for impact abrasion wear cylindrical specimens 10 mm in diameter collided periodically, by impact of their end faces, with an anvil covered with a 14A32NM abrasive cloth. At the moment of collision the abrasive cloth was immobile, i.e., the impact was direct. The impact energy in the tests was 0.5 J.The mechanical properties and the relative wear resistance (K, w )HA and (K~x u )la of the materials tested for hydraulic (HA) and impact (IA) abrasion wear are presented in Table I. In both series of tests the standard specimens were made of carbon steel 25L in a cast state.St. Petersburg State University of Water Communications, St. Petersburg, Russia.The dependence of (K6u)m,, of the materials on their hardness HI'is presented in Fig. la. The points in Fig. 12 can be grouped around four cu~'es corresponding to a power dependence (K,~I.)H A = const I HV",where cons h is a constant and t7 is an exponent varying from 3 to 1.5. In the lower part of Fig. l a we present dependences of the coefficient of rigidity of the stress state P of the studied materials on their hardness for angles of collision ct between the abrasive particles and the worn surface equal to 90 ~ , 45 ~ , and _~ 0 ~ At c~ z 0 ~ the collision betv,,een the particles and the surface of the specimen occur...

Engineering Method for Analysis of the Ability to Strain-Hardening of Steels

“…The ideas about the hardening of metastable austenitic steels make it possible to conclude that the hardening effect is determined by three main factors in the temperature range Ms -Md: 1) austenite strain hardening; 2) quantity, strength and distribution of ε-and α-martensitic phases formed during strain; 3) strain martensite cold-hardening. Due to the fact that the effect of the last two factors, which make a significant contribution to hardening, is inherent only in steels with metastable austenite, these steels have a higher hardening ability than similar stable austenitic steels [3,[12][13][14]. If we consider other factors contributing to strain hardening and stress relaxation, such as solid-solution hardening, energy of stacking faults, twinning, etc., less significant than the formation of strain martensite crystals, which is harder than the original austenite [15].…”

Structure‐energy criterion of the wear resistance of metals and alloys with allowance for the stiffness of the stressed‐strained state of the surface

“…In the process of HA and IA wear the stiffness coefficient of the stressed‐strained state of the surface of the materials, II, was determined using the Tsvetkov's technique (Pogodaev et al , 1997) according to which Π=( σ x + σ y + σ z )/ σ i =1.651 n (3,450/HV), where σ x , σ y , and σ z are the principal stresses acting along the axes X , Y , and Z , respectively; σ i is the stress intensity, and HV is the Vickers hardness measured in megapascals.…”