TS-151
Scuffing Characteristics of Wear Resisting Steel and Steel with Surface Modification Treatment
Kenzo Miura*, Tetsuo Komoda**, Akira Yoshida***,Masahiro Fujii***
ABSTRACT
Wear resisting steel (WRS), improved scuffing characteristics was newly developed in order to apply to the frictional parts for macbinary. The two rollers tests were carried out using the newly developed WRS, steels with Ni-P electroless plating, and with electrolyzed and sulfurizing treatment. Then the scuffing characteristics of these materials were discussed.
The anti-scuffing characteristics of WRS were very good and the friction coefficient was as small as about (1/3) of SUJ2, a reference material. From the test results using WRS specimen of two kinds of hardness, the anti-scaffing characteristics of specimen of which the hardness was low was higher. The anti-scuffing characteristics of steel with Ni-P electroess plating were good. The part of Ni-P electroless plating layer disappeared but the other part of plating layer remained during the test period. The electrolyzed and sulfurizing layer, however, disappeared in a short time, and became that of base material.
According to the observation results of surface and cross section of specimen, the white layer on the cuffing surface existed at 30 to 50 μm thickness. A part of cementite in the slide surface dissolved by thermal energy, and it seemed the formed white layer was the martensite in which carbon dissolved supersaturatedly.
1. INTRODUCTION
Piston ring and cylinder liner of marine diesel engine have been limited to high phosphorus gray cast iron which has the good sliding characteristics though its strength is low. As the mechanical load and the heat load of cylinder sliding materials, piston ring and cylinder liner are increasing with the increase of output ratio of diesel engine, accidental damages such as breakage or sticking which caused by being low strength or not so high anti-scuffing, sometimes occur. Suitable and efficient counter measures are most necessary to improve the reliability and the durability of cylinder sliding material 1).
One of authors developed the low alloy steel, wear resisting steel (the following, WRS) 2) which improved wear resistance and anti-scuffing for the purpose of strengthening, increase of durability and improvement of reliability of the frictional parts for machinery. WRS is relatively high strength, and it possesses over gray cast iron with the good frictional characteristics.
For the low alloy steel, strengthening of the matrix or surface modification treatment has been generally applied in order to improve wear resistance and anti-scuffing. In the frictional parts for machinery, good wear resistance and good anti-scuffing are required, and it is necessary to lower the friction inefficient.
Then, scuffing tests by the two rollers were carried out using the newly developed WRS without and with surface modification treatment in order to evaluate the scuffing characteristics. In this study, scuffing strength and scuffing damage of WRS were examined.
2. SPECIMEN and SURFACE MODIFICATION TREATMENT
2.1 SPECIMEN
Wear resisting steel of the low alloy system is the material with the strong matrix such as martensite or sorbite, and in which hard carbide was precipitated. When lubricating oil breaks off, the adhesive wear is occurred in the short time for these steels which have no self-lubricating, and it develops to the scuffing. Therefore, the excellent wear resistance is expected, if the lubricity is given these steels.
Though the most practical method for giving the lubricity to the material was the precipitaton of graphite, according to the basic test results carried out before, additicn of sulfur and carbide precipitation, etc. were also effective for the self-lubricating. Trace elements such as molybdenum and sulfer were added by compounding to newly developed WRS, and it is a material with comparatively high strength, and frictional characteristics over the high phosphorous gray cast iron.
WRS without and with surface modificaticn treatment are the specimen, and bearing steel JIS-SUJ2 of which the chemical composition was almost same was for the reference material.
* MES Testing & Research Center Co., Lid
** Mitsui Engineering & Shipbuilding Co., Ltd
*** Mechanical Engineering Dept., Okayama University
