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Efficiency and wear properties of spur gears made of powder metallurgy materials
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). (SKD)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Powder metallurgy (PM) is usually used in manufacturing parts with complex geometries, such as gears and structural parts. The main attractions of PM are the high rate of material utilization, environmental friendliness of production, economic advantages (especially for complex geometries), and possibility of obtaining lighter components. To find a wide range of applications and compete with regular steel gears, PM gear transmissions should have good transmission efficiency and wear properties. Furthermore, they should have low contact noise and adequate surface fatigue properties. Because of the porosity structure of PM gears both on gear flanks and in the body, the friction and wear properties of PM gear flank contacts differ somewhat from those of regular steel gears.

   This doctoral thesis examines the efficiency and wear properties of PM gears. Paper A compares the wear, friction, and damage mechanism properties of two sintered gear materials with those of a standard gear material. Paper B deals with the gear mesh torque loss mechanism of PM and regular steel gears by combining both pin-on-disc frictional and FZG efficiency tests. Paper C comparatively examines the efficiency of PM and regular steel gears by conducting FZG gear efficiency tests. Paper D focuses on the wear and friction properties of PM and regular steel gear materials treated using the triboconditioning process. Paper E studies the friction and wear properties attributable to different pore sizes in PM gear materials.

   The results indicate that regular steel meshed with PM gear material and PM meshed with PM gear material are good candidate combinations for gear transmissions. This is because the porosities of PM material can lower the friction coefficient while the wear rate can be the same as or even better than that of regular steel contacts. The triboconditioning process enhances the wear resistance and reduces the friction coefficient of the PM gear material. The friction and wear coefficients of PM meshed with PM gear material display increasing trends with increasing pore size. The friction and wear coefficients of regular steel meshed with PM gear material display decreasing trends with increasing pore size.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. , 125 p.
Series
TRITA-MMK, ISSN 1400-1179 ; 2016:04
Keyword [en]
Powder Metallurgy Gears; Efficiency; Wear; Friction; Porosity Structure; FZG gear test rig
National Category
Tribology
Research subject
Machine Design
Identifiers
URN: urn:nbn:se:kth:diva-187446ISBN: 978-91-7595-963-4 (print)OAI: oai:DiVA.org:kth-187446DiVA: diva2:930150
Public defence
2016-06-03, Galanta, Brinellvägen 83, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160523

Available from: 2016-05-23 Created: 2016-05-23 Last updated: 2016-05-23Bibliographically approved
List of papers
1. A pin-on-disc study of the tribology characteristics of sintered versus standard steel gear materials
Open this publication in new window or tab >>A pin-on-disc study of the tribology characteristics of sintered versus standard steel gear materials
2015 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577Article in journal, Editorial material (Other (popular science, discussion, etc.)) Accepted
Abstract [en]

Though powder metallurgy (PM) allows manufacturing of complex components, including gears, we lack knowledge of the tribological performance of PM versus standard steel gear materials. Using a pin-on-disc machine, we simulate the sliding part of gear tooth contact in boundary and mixed lubricated regions, comparing the tribological characteristics of two sintered gear materials with those of a standard gear material. The comparison considered damage mechanisms, wear, and friction between these materials in different configurations (i.e., standard versus standard, sintered versus sintered, and sintered versus standard). The results indicate that, for pairings of the same gear materials, i.e., RS–RS (16MnCr5), AQ–AQ (Distaloy AQ+0.2% C), and Mo–Mo (Astaloy 85Mo+0.2% C), RS has a lower friction coefficient. For PM and RS combinations, both PM pins have lower friction coefficients with RS disc material than do RS pins with PM disc materials. For the wear coefficient, at low and high speeds, RS pins always display better wear resistance than do AQ or Mo pins because of their high hardness and compacted microstructure. For RS–PM combinations, Mo pins display higher wear resistance than do AQ pins because their larger and more numerous pores enable good lubrication. Pins in the Mo–RS combination displayed the highest wear resistance, mainly because the pores in Mo discs hold lubricant, lubricating the contact surface and preventing adhesive wear. For the RS pin in the Mo–RS combination and the AQ pin in RS–AQ, the damage mechanism is slight adhesive wear and scuffing. For pins in the PM–PM, RS–PM, AQ–RS, and RS–RS combinations, the damage mechanism is a heavier scuffing-type adhesive wear.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Gear material, Powder metallurgy, Wear, Friction, Damage mechanism
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-169932 (URN)10.1016/j.wear.2015.01.032 (DOI)2-s2.0-84922954597 (Scopus ID)
Note

QC 20150714

Available from: 2015-06-25 Created: 2015-06-25 Last updated: 2017-12-04Bibliographically approved
2. FZG gear efficiency and pin-on-disc frictional study of sintered and wrought steel gear materials
Open this publication in new window or tab >>FZG gear efficiency and pin-on-disc frictional study of sintered and wrought steel gear materials
2015 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 60, no 9Article in journal (Refereed) Published
Abstract [en]

Load-dependent power loss is a major contributor to power loss in gear transmission systems. In this study pin-on-disc frictional and FZG efficiency experiments were conducted with powder metallurgy (Distaloy AQ+0.2%C) and wrought material (16MnCr5) combinations. The gear mesh torque loss from gear efficiency tests and the friction coefficient from the pin-on-disc tests were then compared. The trend for both test series was the same. The combination of 16MnCr5 in contact with Distaloy AQ+0.2%C shows the lowest coefficient of friction and gear mesh torque loss, followed by the combination of Distaloy AQ+0.2%C in contact with itself, and finally the combination of 16MnCr5 in contact with itself.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2015
Keyword
Friction, Gear mesh torque loss, Powder metallurgy, FZG gear test rig, Pin-on-disc
National Category
Other Materials Engineering Materials Engineering
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-187439 (URN)10.1007/s11249-015-0582-6 (DOI)000363051300006 ()2-s2.0-84941369781 (Scopus ID)
Note

QC 20160523

Available from: 2016-05-23 Created: 2016-05-23 Last updated: 2017-11-30Bibliographically approved
3. A study of the efficiency of spur gears made of powder metallurgy materials - ground versus super-finished surfaces
Open this publication in new window or tab >>A study of the efficiency of spur gears made of powder metallurgy materials - ground versus super-finished surfaces
2016 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 95, no 1, 211-220 p.Article in journal (Refereed) Published
Abstract [en]

Power loss is one of the main concerns in gear transmission systems. In this study a recirculating power back-to-back FZG test rig was used to investigate the efficiency of spur gears made of powder metallurgy (PM) material using two different surface manufacturing methods (ground and super-finished). The results were compared with previously presented results of standard gear material from the same test rig. The influence of the material (Wrought steel or PM) and surface roughness on the gear mesh efficiency and the total efficiency of the gearbox were analyzed in detail. The Young's modulus for PM materials is lower than for conventional gear steel. This may influence gear tooth bending and the efficiency of the gear transmission. Gear contact simulation results showed that the influence of gear tooth bending on PM gear transmission efficiency can be ignored in the FZG gear geometry. Higher surface energy combined with a smoother surface led to a lower transmission efficiency for the super-finished powder metallurgy gear combination compared to the standard gear material.

Place, publisher, year, edition, pages
Elsevier, 2016
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-179702 (URN)10.1016/j.triboint.2015.11.021 (DOI)000371103400024 ()2-s2.0-84949433501 (Scopus ID)
Note

QC 20160121

Available from: 2015-12-21 Created: 2015-12-21 Last updated: 2017-12-01Bibliographically approved
4. Pin-on-Disc Study of Tribological Performance of Standard and Sintered Gear Materials Treated with Triboconditioning Process: Pre-treatment by Pressure-induced Tribo-film formation
Open this publication in new window or tab >>Pin-on-Disc Study of Tribological Performance of Standard and Sintered Gear Materials Treated with Triboconditioning Process: Pre-treatment by Pressure-induced Tribo-film formation
2016 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397XArticle in journal (Refereed) Accepted
Abstract [en]

oating is one of the innovative approaches used to improve the wear resistance and load-carrying capacity of surfaces in rolling-sliding contact, such as gears and rolling element bearings. In this study, the tribological performance of standard gear material (16MnCr5) and two kinds of powder metallurgy (PM) gear material (Distaloy AQ + 0.2% C and Astoloy 85Mo +0.2% C) with and without tribofilms formed by a pre-treatment were evaluated. Specimens treated with the pre-treatment and the substrate is subjected to pin-on-disc tests under boundary lubrication conditions. The friction and wear performance of the two different PM gear materials with the pre-treatment formed tribo-film were compared to RS-RS (16MnCr5 material disc and pin combination) for reference. It was found that the pre-treatment lowers the friction coefficient and enhances the wear resistance of pins because of the tribo-film formed. The tribo-film caused good running-in due to the existing of  and Fe and W oxides. Mo-Mo (Astoloy 85Mo + 0.2% C material disc and pin combination) and Mo-RS (Astoloy 85Mo + 0.2% C disc and 16MnCr5 pin combination) showed statistically significant higher wear resistance.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2016
Keyword
Gear material, Powder metallurgy, Pre-treatment, Wear, Friction
National Category
Tribology
Research subject
Industrial Engineering and Management
Identifiers
urn:nbn:se:kth:diva-187443 (URN)10.1080/10402004.2016.1146379 (DOI)
Note

QC 20160523

Available from: 2016-05-23 Created: 2016-05-23 Last updated: 2017-11-30Bibliographically approved

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