Accession Number : AD0727659

Title :   Fatigue Properties of Investment Castings.

Descriptive Note : Technical rept.,

Corporate Author : IIT RESEARCH INST CHICAGO ILL

Personal Author(s) : Shaw,William F. ; Watmough,Thomas ; O'Shea,Robert P. ; Dorcic,J. ; Staschke,J.

Report Date : APR 1971

Pagination or Media Count : 32

Abstract : Large numbers of investment castings are being utilized as components in weapons. Because of the precision of these castings, many of the surfaces exposed to fatigue stresses are cast surfaces. The material studied was an AISI 4140 steel in both the cast and forged condition. Results established that the endurance ratio for the forged material in tension-tension fatigue is 0.54 while the potential ratio for the equivalent cast material is 0.47, very close to that of the forged alloy. Also, the presence of an oxide surface condition, designated as oxide folds, could lower this ratio to as low as 0.24, depending on the severity of these folds. The oxide folds were generally influential enough to mask any effects that surface finish, decarburization, or defects resulting from refractory inclusions might have on fatigue. The work has suggested that process modifications which minimize the oxide film condition will permit the potential endurance ratio to be realized. The addition of a reducing agent to the investment molds is one method noted in this work. Additionally, the work suggested that improvements in endurance ratio in castings which have oxide folds on the surface may also be achieved by abrasive blasting. Fatigue data on investment castings, previously unavailable, have been generated for use in design applications, and the conditions affecting fatigue properties of the castings have been more clearly delineated. (Author)

Descriptors :   (*CASTINGS, FATIGUE(MECHANICS)), STEEL, IMPURITIES, DEFECTS(MATERIALS)

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE