Weldability test determines the effects of material and process variables on the occurrence of strain-age cracking, and demonstrates effective and practical means for its reduction. Studies consist of tensile, impact, and stress-rupture tests

Prager, M.

Thompson, E. G.

English

NASA Technical Reports Server

November 1969	 Brief 69-10605 
NASA TECH BRIEF 
NASA Teèh Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Strain-Age Cracking in Rene 41 Alloy 
A reliable weldability test has been developed to 
investigate strain-age cracking in batches of the 
alloy Rene 41. This test has been used to determine 
the effects of material and process variables on the 
occurrence of this serious defect, and to demonstrate 
effective and practical means for reducing the extent, 
of strain-age cracking. 
Two welding studies, consisting of tensile, impact, 
and stress-rupture tests, were conducted. As far as 
possible, the same material was used in both studies, 
in order to allow direct comparison of results. Material 
and process variables considered were: solution-
annealing temperature, time, and number of cycles; 
cooling rate; aging temperature;. and alloy carbon 
content. Alloy characteristics of primary interest 
were ductility and toughness. Deviations from normal 
processing which resulted in either impaired or en-
hanced durability were noted. 
Strain-age cracking resistance of each batch of 
Rene 41 may now be determined prior to its introduc-
tion into the manufacturing process. Evaluations may 
be performed with a controlled-heating-rate tensile 
test or a weld-circle patch test. 
Low ductility in high-temperature air is the main 
factor contributing to strain-age cracking. Batches 
with less than two percent minimum elongation 
yield unsatisfactory results. Low carbon batches 
(less than 0.06%) show poor weldability, low ductility, 
and low toughness after aging. At 1400°F, the 
ductility of these batches averages two-thirds that of 
normal material. 
When subjected to a rapid pre-aging- cooling rate 
(up to 45°F/mm), Rene 41 alloy shows improved
toughness and ductility over a wide range of elevated 
temperatures. 
Strain-age cracking resistance as well as the critical 
mechanical properties of toughness and ductility are 
improved by modification of the size, type, and distri-
bution of the grain-boundary carbide particles and of 
the -y precipitate. This is accomplished by using a 
pre-weld heat treatment and by performing post-weld 
annealing under an inert atmosphere. 
One promising area for further investigation would 
involve the relationship between the type of heat-
treating atmosphere and the amount of strain-age 
cracking. 
Notes: 
1. Information in a related field, investigation of 
strain-age cracking by electron microscopy, is pre-
sented in Rocketdyne report No. 66-20 (N69-
71272). 
2. For additional information write to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B69-10605 
Patent status: 
No patent action is contemplated by NASA. 
Source: Ernest G. Thompson and Martin Prager of 
North American Rockwell Corporation 
Rocketdyne Division 
under contract to 
Marshall Space Flight Center 
(MFS-18650) 
Category 03 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
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Strain-age cracking in Rene 41 alloy

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