耐摩耗鋳鉄の焼付き性と摩耗特性に及ぼす黒鉛および共晶炭化物の影響

Abstract

Seizure tests were carried out on Ni-Cr-Mo abrasion resistant cast irons containing different amounts of graphite and eutectic carbides. Specimens were prepared with changing Cr and Ni contents based on 2.3% C-1.5% Si- 0.6 Mn- 1.8 Mo iron. Surfaces of the test pieces were finished with mechanical grinding or electro-spark machining up to roughness of Ra:0.30 ~ 0.35. Seizure properties were evaluated with using a high peripheral speed wear tester. Higher load was applied for evaluating seizure property, while lower load was applied for friction coefficient. Weight loss was also measured after testing. Surfaces of the specimen after seizure test were observed with SEM. The specimens with higher amounts of graphite showed lower friction at the early stage of seizure tests. When the testing load was increased, seizure was significantly occurred on the specimen with graphite. The effect of graphite for lubrication was also diminished in the case of wear tests under lower load except the early stage of testing. The electro-spark machining for surface finishing lead to exfoliation of graphite from the surface resulting in increase in friction coefficient. The specimen with higher amount of carbides showed superior wear properties.