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Fretting corrosion caused by vibration with stationary rolling bearings
Since wear of prototype surfaces is known to range from (a) plastic deformation resulting from scratches and scores to (b) fatigue spalling, the testing machine was operated to reproduce typical scratches and craters, as well as hardness changes. Results indicate that highest work-hardening occurs in regions of maximum wear, and reveal other details concerning the angle of the specimen, reproducibility, order of effectiveness of various facing materials, and potential application of the method to other types of wearing surfaces. Some Aspects of the Effects of the Structural Type of Two Aluminium Alloys on Their Sliding and Wear Resisting Performance.
Gh. Vasilca, Al. Nica, 0. Hita and I. Dinca, Rev. Roumaine Sci. Tech. Se?. Me’canique Appl., 9 (5) (1964) 1oS5-1100; 6 plates. This review describes studies on an A-Sb alloy with hard inclusions of AlSb in a semhard matrix of Al solid solution and on an Xl-% alloy with a semi-hard matrix of Al solid solution and soft inclusions of Sn. The Wear of Diamond. 3f. Seal, Ind. Diamond Rev.. (1965) 111-116; 4 figs., I table, 22 refs. Experiments associated the wear of diamonds at low sliding speeds with the formation of small quantities of a debris in the region surrounding each track. The author favours the theory that the wear is due to attrition on a very small scale, the fragments losing their identity as diamond due to the presence of absorbed gas. Studies of Wear and Load-carrying Capacity in the Pin and Disk Machine. W. G. Robertson, ASLE Tmns., 8 (1965) in press; Paper No. 64 LC-14; tt figs., rg refs. A pin and disk machine has been used to investigate the influence of load and stress on the wear of steel specimens lubricated with a plain mineral oil and two blends containing typical commercial EP additives. Under constant load conditions it was found that, contrary to the wear law of Archard et al., the volume wear rate decreased asymptotically to zero throughout each test. With each additive blend the final stress was found to be a constant irrespective of the load applied, whereas with the base oil the final stress increased as the applied load was increased. It is suggested that for the additive blends the mechanism of lubrication is boundary, but that with the base oil a hydrodynamic oil-film is formed. The importance of these results is that they show that, under such lubricated conditions, the equilibrium state is not one of steady wear, as previously thought, but one of zero Wear, 8 (1965) 4o7-419
wear and that wear should properly 1~ thought of as a transient process, It is sho\rn that once the existence of the equilibrium state is recognized this transient u car can 1~~ expressed to a good approximation b>- ;I simple modification of the dry wear law. The Friction
and Wear Behavior of Molybdenum-Tungsten-Chromium Alloys in Hightemperature Sodium Environments.
W. H. Roberts, AXE Trans., 8 (rgo5j in press; Paper No. (~4 1X-25; rz figs., 2 tables. 22 refs. Friction and wear data, obtained with a crossed-cylinders apparatus, are presentcd for a selection of molybdenum--tungsten chromium alloys, over the temperature range zoo--5oo’C, for two sodium environments : the molten metal, containing approximately 5 p.p.m. of oxygen impurity, and pure argon containing sodium vapor at concentrations corresponding with the temperature equilibrium value. Some comparisons are made with results obtained in gaseous environments of pure argon, helium, and carbon dioxide. >An indication is given of the effect on friction and wear behavior of increasing the oxygen content in liquid sodium from about 5 to 80 p.p.m. It was concluded that chemisorbed doublcoxide films, formed by reaction of the molybdenum, tungsten, and chromium constituents of the alloys with the sodium environment, play a significant role in providing boundary lubrication in high-temperature sodium. Also, the effectiveness of the lubrication provided by such films is a function of the specific nature of the sodium environment (vapor or molten state), and temperature, as well as time at temperature. Fretting Corrosion Caused by Vibration with Stationary Rolling Bearings. H. Pittroff, J. Basic Enf., Sept. rg6j,
ASME Paper No. 64-Lub-zr ; IO figs., 16 refs. If nonrotating rolling bearings are exposed to vibration then the raceways especially in roller bearings can be damaged in a short time. False brinelling in bearings is caused by fretting corrosion. All research in this area therefore belongs to the field of fretting corrosion. Owing to the alternating elastic deformation in the contact area between the rolling elements and the raceway as well as to the shearing strength being exceeded in the microcontact area, surface particles are abradoxidized. ccl, which become immediately The kind and the extent of damage primarily depend on the static load of the bearings. The resistance to false brinelling can be increased by means of lubricants and surface treatments. It is possible to give limits for the admissible flute characteristics. In cases of already known vibration characteristics the
LXTERATURE AND CURRENT EVENTS time of the bearing failure matically predetermined.
can be mathe-
Roliing+contact Studies with Four Refrace torv Materials to 2000°F. R. j. Parker, S. J.Grisaffe and E. ‘v. Zaretsky, ASLE Trans., 8 (1965) ~ - _. in Dress: Paper No. 64 LC-z8 ; Q figs., 2 tables, 17*refs. _ Four refractory materials were tested in the five-ball fatigue tester to study their behavior under repeated stresses applied in rolling contact: hot-pressed alumina, coldpressed-and-sintered alumina, self-bonded silicon carbide, and nickel-bonded titanium carbide cermet. The failures that developed in all four materials were shallow. eroded areas of apparent surface origin unlike fatigue spalls found in bearing steels. The load capacity of hot-pressed alumina was the highest of the four materials tested but was o&y about 7% of that of a typical bearing steel. Preliminary tests at elevated temperatures indicated that hot-pressed alumina is capable of rolling-contact operation at temperatures up to 2000°F without gross wear or plastic deformation. Wear Due to the Microslip Between a Rolling Body and Its Track. J. Halling and 3. G. Brothers, J. Basic Eng., Sept. 1965, in press; ASME Paper 64-Lub-so; I I figs., IO refs. The paper describes an experimental study of the wear in the contact zone between a rolling ball and its track. The ball is subjected to a normal load and a small resisting torque and the rate of wear resuiting from the ensuing microslip was determined using a radioactive tracer technique. The effect of load, speed, hardness and surface finish have been investigated, the latter property having negligible effect on the resuits. The results have been used to obtain the equivalent macroscopic sliding wear law which is found to deviate from that normally associated with mild galling wear. Tentative suggestions for this discrepancy are proposed. The Use of Radioactive Tracers in the Study of Wear Arising from Microslip Between Rolling Bodies. B. G. Brothers and J. Hailing, B&t. J. A#JI. p&S., 15 (1964) 14X5-1421. 6. TEST METHODS AND TESTING A Rotating Sphere, Absolute Vacumn Gauge. P. J. Karbour and R. G. Lord, J. Sci. I&v., qa (x965) IOJ-108; 5 figs., g refs. This naper describes a linear hiah-vacuum gauge- which is absolute if the-molecular weight of the gas is known. It consists of a magnetically suspended rotating sphere
4x7 which decelerates because of gaseous drag the deceleration being directly proportional to the pressure. Since the magnetic bearing used is almost frictionless, the torque on the rotor is caused almost entirely by gaseous drag: other sources of drag-electromagnetic interactions, cooling of the rotor and residual vapours in the vacuumsystem-can be made sufficiently small not to affect calibration results. If, for a constant rotor speed, the pressure in the system is increased, then the torque increases linearly with pressure. This rate of increase of torque with pressure is calculated methods of kinetic by well-established theory, assuming the tangential momentum coefficient of the surface to be unity: there is good experimental evidence for this assumption. 33~ measuring the deceleration as a function of pressure on an ionization gauge the method could be used to calibrate the ionization gauge with an absolute accuracy to about 3% for any gas. (See also F. P. Bowden and R. G. Lord, Wear, 8 (1965) 73.) Measurement of Refractive Index and Dispersion of Mica, Employing Multiple Beam Interference Techniques. A. 1. Bailey and Susan M. Kay, &it. J. A$$. Phys., 16 (1965) 39-44; 5 figs., z plates, 4 refs. It is sometimes impossible to make measurements of the refractive index of a solid using an Abbe refractometer. Under these circumstances simple and accurate measurements can be made tlrv immersinz the solid in a liquid whose refractive index can be varied until it matches that of the solid. This paper describes methods which ensure thai the match is made to a high degree of accuracy. Multiple beam interference fringes are sensitive to small changes in refractive index and examination of Fizeau fringes formed by light passing through the solid and through the liquid only, reveals such small changes. Heating or cooling of the liquid then enables the match to be made exactly. By determining the dispersion of the immersion fluid, fringes of equal chromatic order provide a simple and quick method for obtaining the dispersion of a solid. An Eiectron Microscope Study of Rolling Contact Fatigue. G. S. Reichenbach and W. D. Syniuta, ASLE Trans., 8 (1965) in press; Paper No. 64 LC-zg; 9 figs., 8 refs. Progressive changes in the surface topography of the running track in a rolling contact fatigue tester were studied by using replica techniques and the electron microscope. Early in the life of a specimen, micronsize cracks appeared on the stressed surface. With further running more cracks appeared, Wear. 8 (1965) 407-419
Gh. Vasilca, Al. Nica, 0. Hita and I. Dinca, Rev. Roumaine Sci. Tech. Se?. Me’canique Appl., 9 (5) (1964) 1oS5-1100; 6 plates. This review describes studies on an A-Sb alloy with hard inclusions of AlSb in a semhard matrix of Al solid solution and on an Xl-% alloy with a semi-hard matrix of Al solid solution and soft inclusions of Sn. The Wear of Diamond. 3f. Seal, Ind. Diamond Rev.. (1965) 111-116; 4 figs., I table, 22 refs. Experiments associated the wear of diamonds at low sliding speeds with the formation of small quantities of a debris in the region surrounding each track. The author favours the theory that the wear is due to attrition on a very small scale, the fragments losing their identity as diamond due to the presence of absorbed gas. Studies of Wear and Load-carrying Capacity in the Pin and Disk Machine. W. G. Robertson, ASLE Tmns., 8 (1965) in press; Paper No. 64 LC-14; tt figs., rg refs. A pin and disk machine has been used to investigate the influence of load and stress on the wear of steel specimens lubricated with a plain mineral oil and two blends containing typical commercial EP additives. Under constant load conditions it was found that, contrary to the wear law of Archard et al., the volume wear rate decreased asymptotically to zero throughout each test. With each additive blend the final stress was found to be a constant irrespective of the load applied, whereas with the base oil the final stress increased as the applied load was increased. It is suggested that for the additive blends the mechanism of lubrication is boundary, but that with the base oil a hydrodynamic oil-film is formed. The importance of these results is that they show that, under such lubricated conditions, the equilibrium state is not one of steady wear, as previously thought, but one of zero Wear, 8 (1965) 4o7-419
wear and that wear should properly 1~ thought of as a transient process, It is sho\rn that once the existence of the equilibrium state is recognized this transient u car can 1~~ expressed to a good approximation b>- ;I simple modification of the dry wear law. The Friction
and Wear Behavior of Molybdenum-Tungsten-Chromium Alloys in Hightemperature Sodium Environments.
W. H. Roberts, AXE Trans., 8 (rgo5j in press; Paper No. (~4 1X-25; rz figs., 2 tables. 22 refs. Friction and wear data, obtained with a crossed-cylinders apparatus, are presentcd for a selection of molybdenum--tungsten chromium alloys, over the temperature range zoo--5oo’C, for two sodium environments : the molten metal, containing approximately 5 p.p.m. of oxygen impurity, and pure argon containing sodium vapor at concentrations corresponding with the temperature equilibrium value. Some comparisons are made with results obtained in gaseous environments of pure argon, helium, and carbon dioxide. >An indication is given of the effect on friction and wear behavior of increasing the oxygen content in liquid sodium from about 5 to 80 p.p.m. It was concluded that chemisorbed doublcoxide films, formed by reaction of the molybdenum, tungsten, and chromium constituents of the alloys with the sodium environment, play a significant role in providing boundary lubrication in high-temperature sodium. Also, the effectiveness of the lubrication provided by such films is a function of the specific nature of the sodium environment (vapor or molten state), and temperature, as well as time at temperature. Fretting Corrosion Caused by Vibration with Stationary Rolling Bearings. H. Pittroff, J. Basic Enf., Sept. rg6j,
ASME Paper No. 64-Lub-zr ; IO figs., 16 refs. If nonrotating rolling bearings are exposed to vibration then the raceways especially in roller bearings can be damaged in a short time. False brinelling in bearings is caused by fretting corrosion. All research in this area therefore belongs to the field of fretting corrosion. Owing to the alternating elastic deformation in the contact area between the rolling elements and the raceway as well as to the shearing strength being exceeded in the microcontact area, surface particles are abradoxidized. ccl, which become immediately The kind and the extent of damage primarily depend on the static load of the bearings. The resistance to false brinelling can be increased by means of lubricants and surface treatments. It is possible to give limits for the admissible flute characteristics. In cases of already known vibration characteristics the
LXTERATURE AND CURRENT EVENTS time of the bearing failure matically predetermined.
can be mathe-
Roliing+contact Studies with Four Refrace torv Materials to 2000°F. R. j. Parker, S. J.Grisaffe and E. ‘v. Zaretsky, ASLE Trans., 8 (1965) ~ - _. in Dress: Paper No. 64 LC-z8 ; Q figs., 2 tables, 17*refs. _ Four refractory materials were tested in the five-ball fatigue tester to study their behavior under repeated stresses applied in rolling contact: hot-pressed alumina, coldpressed-and-sintered alumina, self-bonded silicon carbide, and nickel-bonded titanium carbide cermet. The failures that developed in all four materials were shallow. eroded areas of apparent surface origin unlike fatigue spalls found in bearing steels. The load capacity of hot-pressed alumina was the highest of the four materials tested but was o&y about 7% of that of a typical bearing steel. Preliminary tests at elevated temperatures indicated that hot-pressed alumina is capable of rolling-contact operation at temperatures up to 2000°F without gross wear or plastic deformation. Wear Due to the Microslip Between a Rolling Body and Its Track. J. Halling and 3. G. Brothers, J. Basic Eng., Sept. 1965, in press; ASME Paper 64-Lub-so; I I figs., IO refs. The paper describes an experimental study of the wear in the contact zone between a rolling ball and its track. The ball is subjected to a normal load and a small resisting torque and the rate of wear resuiting from the ensuing microslip was determined using a radioactive tracer technique. The effect of load, speed, hardness and surface finish have been investigated, the latter property having negligible effect on the resuits. The results have been used to obtain the equivalent macroscopic sliding wear law which is found to deviate from that normally associated with mild galling wear. Tentative suggestions for this discrepancy are proposed. The Use of Radioactive Tracers in the Study of Wear Arising from Microslip Between Rolling Bodies. B. G. Brothers and J. Hailing, B&t. J. A#JI. p&S., 15 (1964) 14X5-1421. 6. TEST METHODS AND TESTING A Rotating Sphere, Absolute Vacumn Gauge. P. J. Karbour and R. G. Lord, J. Sci. I&v., qa (x965) IOJ-108; 5 figs., g refs. This naper describes a linear hiah-vacuum gauge- which is absolute if the-molecular weight of the gas is known. It consists of a magnetically suspended rotating sphere
4x7 which decelerates because of gaseous drag the deceleration being directly proportional to the pressure. Since the magnetic bearing used is almost frictionless, the torque on the rotor is caused almost entirely by gaseous drag: other sources of drag-electromagnetic interactions, cooling of the rotor and residual vapours in the vacuumsystem-can be made sufficiently small not to affect calibration results. If, for a constant rotor speed, the pressure in the system is increased, then the torque increases linearly with pressure. This rate of increase of torque with pressure is calculated methods of kinetic by well-established theory, assuming the tangential momentum coefficient of the surface to be unity: there is good experimental evidence for this assumption. 33~ measuring the deceleration as a function of pressure on an ionization gauge the method could be used to calibrate the ionization gauge with an absolute accuracy to about 3% for any gas. (See also F. P. Bowden and R. G. Lord, Wear, 8 (1965) 73.) Measurement of Refractive Index and Dispersion of Mica, Employing Multiple Beam Interference Techniques. A. 1. Bailey and Susan M. Kay, &it. J. A$$. Phys., 16 (1965) 39-44; 5 figs., z plates, 4 refs. It is sometimes impossible to make measurements of the refractive index of a solid using an Abbe refractometer. Under these circumstances simple and accurate measurements can be made tlrv immersinz the solid in a liquid whose refractive index can be varied until it matches that of the solid. This paper describes methods which ensure thai the match is made to a high degree of accuracy. Multiple beam interference fringes are sensitive to small changes in refractive index and examination of Fizeau fringes formed by light passing through the solid and through the liquid only, reveals such small changes. Heating or cooling of the liquid then enables the match to be made exactly. By determining the dispersion of the immersion fluid, fringes of equal chromatic order provide a simple and quick method for obtaining the dispersion of a solid. An Eiectron Microscope Study of Rolling Contact Fatigue. G. S. Reichenbach and W. D. Syniuta, ASLE Trans., 8 (1965) in press; Paper No. 64 LC-zg; 9 figs., 8 refs. Progressive changes in the surface topography of the running track in a rolling contact fatigue tester were studied by using replica techniques and the electron microscope. Early in the life of a specimen, micronsize cracks appeared on the stressed surface. With further running more cracks appeared, Wear. 8 (1965) 407-419