Ni-hard 의 내마모성에 관한 연구 = Studies on the Abrasive Wear Resistance of Ni-hard

국문 초록 (Abstract)

Ni-hard의 凝固後 冷却速度가 耐磨耗性에 미치는 影響이 考察되었다. 또한 殘留 austenite가 tempering에 依하여 bainite로 變態되었을 境遇 耐磨耗性에 미치는 影響도 考察되었다.
本 實驗의 結果에 依하면 Ni-hard는 凝固後 徐冷이 始作되는 溫度가 上昇될수록 硬度도 上昇하며 約 650℃에 이르면 冷却途中 austenite內의 炭素濃度가 平衡狀態에 到達하여 殘留 austenite가 最少가 되며 따라서 最高硬度에 이르게 되는 것으로 보인다.
殘留 austenite를 tempering에 依하여 bainite로 變態시키면 一般的으로 硬度의 增加가 나타나나 磨耗時 磨耗表面에서 殘留 austenite의 martensite 變態가 나타날 수 없으므로 耐磨耗度는 오히려 떨어진다고 보인다.
Scratch test에 依하여 grain size가 耐磨耗性에 미치는 影響을 조사한 結果 旣存 磨耗式은 다음과 같이 變形되어질 수 있으리라 보인다.
V= (K"W·L/H)·1/N^¼

다국어 초록 (Multilingual Abstract)

After solidification Ni-hard, the effects of cooling rate on abrasive wear resistance are investigated. When most of retained austenite is transformed to bainite by tempering, the change of abrasive wear resistance is also investigated.
The heardess of Ni-hard increases with increasing the temperature from which slow cooling begins. But the hardness remains at the maximum value even though the temperature gets over about 650℃. This may mean that when the temperature is about 650℃ or above, the carbon concentration of austenite comes to be near equilibrium.
By tempering, retained austenite is transformed to bainite and hardness is increased. But the wear resistance of this transformed Ni-hard is lower than that of original one. It may be because of the fact that the transformed Ni-hard has much less retained austenite to be transformed to martensite by wear at abrading surface than original one.
Using scratch test, the effect of grain size to wear resistance was investigated. As a result, the existing abrasive formula may be modified as follow:
V= (K"W·L/H)·1/N^¼
N : numoer of carbide or aggregate grains in a unit area of wear surface.