Analysis was made to determine correlation between number and size of carbide particles and rolling-element fatigue. Correlation was established, and carbide factor was derived that can be used to predict fatigue life more effectively than such variables as heat treatment, chemical composition, and hardening mechanism

Chevalier, J. L.

Zaretsky, E. V.

English

NASA Technical Reports Server

March 1973
	
B73-10008 
NASA TECH BRIEF 
•	 Lewis Research Center	 ". 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT. Washington, D.C. 20546. 
CARBIDE FACTOR PREDICTS ROLLING-ELEMENT BEARING FATIGUE LIFE 
The Problem: 
To determine the effect of the carbide constituent on 
the fatigue life of rolling-element bearings. Previous 
research has shown that rolling-element fatigue life de-
creases as the total amount of alloying elements such as 
molybdenum, chromium, vanadium, tungsten, and cobalt 
increased. Recent transition from AISI 52100 steel to the 
more highly alloyed tool steels (AISI M-1, M-2, M-10, 
M-42, M-50, 1-1 and Halmo) has resulted in greater 
dimensional stability, retention of hot hardness, wear 
resistance, and oxidation resistance at high temperature, 
but fatigue life has lessened. Most of the alloying elements 
are strong carbide formers: it was felt that an interrelation 
might exist between the number and size of carbide 
particles and rolling-element fatigue life. 
The Solution: 
An analysis was made to determine if a correlation 
does exist between the number and size of carbide 
particles and rolling-element fatigue. Such correlation was 
established, and a carbide factor was derived that can be 
used to predict fatigue life more effectively than such 
variables as heat treatment, chemical composition and 
hardening mechanism. 
How It's Done: 
The materials analyzed were consummable-electrode, 
vacuum-melted (CVM) AISI 52100, AISI-M-1, M-2, M-10, 
M-42, M .50, AISI T-1, and Halmo. Groups of 12.7 mm (ii 
inch) diameter balls of each material were first tested in a 
five-ball fatigue tester, at a maximum Hertz stress of 5.52 
x 109 newtons per square meter (800,000 psi), a contact 
angle' of 300 , and a shaft speed of 10,300 rpm to 
determine the fatigue life. Tests were run at a race 
temperature of 340 K (150°F) with a super-refined 
naphthenic mineral oil as the lubricant. For each of the 
eight materials, three lots were tested. Each test group of 
five balls was taken from a single lot. From 25 to 30 
five-ball tests were run for each material lot. Each test run 
was terminated when either an upper-test ball or a 
lower-test ball failed, or at 100 hours. The test results of 
the three lots of each material were combined, and a
Weibull analysis was performed on the combined results 
to determine the 10-percent fatigue life of each of the 
materials. 
From each material lot, one test ball was chosen at 
random, mounted, metallographically polished, and 
etched. Each ball was then examined on a Quantimet 
Image Analyzing Computer (QTM) to determine the total 
number of carbide particles in a unit area, particle size, 
and percent carbide area in a unit area. 
Essentially, the QTM projects a microscope image on a 
vidicon tube and scans it electronically. Differences in 
optical density are detected, recorded, and processed to 
read out the size of the discriminated (carbide particle) 
area in percent of the measured surface, the number of 
particles in the field of view, and the mean and median 
sizes of the particles. 
Five areas were examined on each sample ball. Four 
areas were near the surface and 90 0 apart; the fifth area 
was near the center of the ball. The values obtained were 
averaged to obtain what was considered the average value 
of the variables for each of the eight materials tested. 
From the test data and a statistical analysis, a carbide 
factor, C, was derived that was capable of predicting the 
rolling-element fatigue lives of the materials investigated 
within an acceptable variance. The carbide factor is 
determined from the following formula: 
3 
C=
M	 718	 a 
0.26 + n + 9.54 + 4Co 
where a = percent area of carbides 
M = median carbide particle size (length) 
n = total number of carbide particles per unit area 
Co = weight percent cobalt 
S(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19730000008 2020-03-17T06:39:23+00:00Z
The correlation coefficient for the prediction of the 
rolling-element fatigue lives for the materials tested was 
between 83 and 87%. 
Notes: 
1. The carbide parameter may also be applicable to 
predicting other types of fatigue (i.e., bending, ro-
tating-bending, etc.). 
2. The following documentation may be obtained from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: NASA TN-D-6835 (N72-26407), Effect 
of Carbide Size, Area, and Density on Rolling-
Element Fatigue 
Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B73.10008 
Patent Status: 
NASA has decided not to apply for a patent. 
Source: J. L. Chevalier
U.S. Army Air Mobility R&D Laboratory,

and E. V. Zaretsky
Lewis Research Center
(LEW-1 1940)
n 
B73-10008	 Category 07


Carbide factor predicts rolling-element bearing fatigue life

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