AGMA 02FTM7-2002 pdf free.Selecting the Best Carburizing Method for the Heat Treatment of Gears by: G.D. Lindell, Twin Disc, Inc., D.J. Breuer, Metal Improvement Company, Inc., D.H. Herring, The HERRING GROUP, Inc.
HISTORICAL BACKGROUND
It is unfortunate that atmosphere and vacuum technology are viewed as competitors instead of as complements to one another. The existing “us versus them”” mentality created by constant negative comparisons has hurt both technologies. In the 1960s the need for better atmosphere control prompted a series of R&D efforts to find a solution. One of these led to the development of vacuum carburizing, viewed as an alternative to atmosphere carburizing providing enhanced metallurgical properties and shorter cycle times, However, it was promoted within the heat treatment industry as a panacea for all the problems of atmosphere carburizing, and, thus, initiated competition between the two technologies.
Had vacuum carburizing proved to be a robust technology at that time, it is generally believed that a significant portion of today’s installed equipment base would use this technology. Its failure to achieve commercial success can be directly related to reliability and cost. The creation of soot was the Achilles heel of vacuum carburizing. Perhaps a more accurate statement is that the equipment designs and process parameters of vacuum carburizing were not optimized, and the technology’s capabilities oversold to the heat-treating community.
Today these problems have been addressed and sooting is no longer a limitation of the process. New equipment designs, controls, and processing methods assure excellent up time productivity and high volume capacities.
POWER TRANSMISSION COMPONENTS
The application and manufacture of high quality transmission gearing used in demanding applications such as shown in Figures 3 and 4 require careful consideration of a number of critical factors including: component design; material selection: heat treatment method; and the influence of post heat treatment manufacturing operations.
Gearing Is subject to both sliding and rolling contact stresses on the gear flanks in addition to bending stress in the tooth roots. The most desirable gear properties to meet these two criteria would be hardened gears for strength and contact properties with residual compressive surface stress for bending fatigue properties.
Fatigue is a major cause of failure in gears. Fatigue failures fall into two classes: tooth root bending fatigue and tooth flank contact related failures. In this work residual stress and microhardness testing were used as indicators to compare the atmosphere and vacuum carburizing processes.
The greater the magnitude and depth of compressive stress the greater the ability to improve fatigue properties. A high compressive stress value at the surface helps the component resist crack initiation. The deeper the compressive layer the greater the resistance to crack growth for longer periods of time.AGMA 02FTM7 pdf download.
AGMA 02FTM7-2002 pdf free
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