1997 Fiscal Year Final Research Report Summary
A STUDY ON THE FATIGUE RELIABILITY OF THERMALLY SPRAIED MATERIAL
| Project/Area Number |
07405008
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | KEIO UNIVERSITY |
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Principal Investigator |
SHIMIZU Masao KEIO UNIV., MECHANICAL ENGINEERING, PROFESSOR, 理工学部, 教授 (90051565)
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| Co-Investigator(Kenkyū-buntansha) |
NOGUCHI Hirohisa KEIO UNIV., MECHANICAL ENGINEERING, ASSOCIATE PROFESSOR, 理工学部, 助教授 (70218303)
KOMOTORI Jun KEIO UNIV., MECHANICAL ENGINEERING, ASSOCIATE PROFESSOR, 理工学部, 専任講師 (30225586)
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| Project Period (FY) |
1995 – 1997
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| Keywords | FATIGUE / SURFACE MODIFICATION / THERMAL SPRAYING / FUSING / POROSITY / 再溶融処理 |
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| Research Abstract |
Since a thermally sprayd coating has high wear, corrosion and heat resisance, it is used in many engineering fields for surface reinforcement and for repair of machine parts such as paper mill rolls, shafts and large bearings. With an increasing demand for the application of this process in several industries, it has become important to clarify the fatigue resistance of thermally sprayd steel. However, many problems remain unsolved concerning the fatigue properties of thermally sprayd coatings.
In this study, the characteristics of the fatigue life of a thermally sprayd specimen with Co-based self-fluxing alloy were examined. The effects of the interface conditions on the sprayd specimen's fatigue strength were also studied. Rotational-bending fatigue tests were carried out to clarify the effect of post heat treatment (fusing treatment) on the fatigue strength of a sprayd specimen. The fatigue fracture mechanisms of thermally sprayd specimens were also examined using a Scanning Electron
… More
Microscope.
The rusults are summarized as follows :
(1) Fusing treatment temperature, heating rate and holding time strongly affect the characteristics of sprayd coatings such as configuration of microstructure, hardness and volume fraction of micro-pore (porosity).
(2) Adhesion strength of thermally sprayd specimens which are fused by using a induction heating system is governed by mechanical interaction. Howver, in the case of a sprayd specimen fused by using a vacuum furnace, the diffusion of chemical elements strongly affects the characteristics of interface and adhesion strength.
(3) There is considerable scatter in the value of porosity for torch-fused specimens. However, it is possible to achieve high quality coatings through well controlled fusing by using an induction heating system. In this case, the scatter of fatigue lives is much smaller than that of a torch-fused specimen.
(4) The fatigue fracture mechanisms of thermally sprayd specimens are described as follows : (i) a crack start at the point of interface, (ii) the crack growth to the substrate (iii) the crack spreads from the interface in the sprayd coating and the entire coating fails rapidly (iv) the remaining part of substrate fails as a result of the coating failure. Less
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