브로칭 가공된 회주철 소재 표면의 마찰 및 마모 특성

Friction and Wear Characteristics of Gray Cast Iron Surface Processed by Broaching Method

Abstract

In this work the friction and wear characteristics of the gray cast iron surface processed by broaching method, which is widely used in the machinery industry, were investigated. The broaching process is mainly used for mass production because it has high dimensional accuracy and processing speed, but the defects on surface can be easily generated. In order to improve the tribological characteristics, the approach was to reduce the roughness and hardness of the surface by adding a machining process to the broaching specimen. The secondary machining process using abrasive grains produces low roughness and hardness than broaching because it has high tool accuracy and removes the work hardened surface. The friction coefficient and the wear rate were assessed using a reciprocating-type tribotester to analyze the effects of surface finishing on the tribological properties. The friction tests were conducted under dry and lubricated conditions. The test results showed that the reduction of surface roughness and hardness through secondary machining process in lubricated condition improved the friction and wear characteristics. The reason why the same results did not appear in a dry condition was that wear occurred more rapidly than in lubricated condition. Thus, the positive effect of roughness and hardness of the surface obtained through the secondary machining process was not observed.

Fig. 1. Schematic of broaching processing.

Fig. 1. Schematic of broaching processing.

Fig. 2. Structure of rotary compressor pump.

Fig. 2. Structure of rotary compressor pump.

Fig. 3. Stress distribution of cylinder slot.

Fig. 3. Stress distribution of cylinder slot.

Fig. 4. Experimental set-up of ball-on-plate friction test.

Fig. 4. Experimental set-up of ball-on-plate friction test.

Fig. 5. Bearing area curve of cylinder slot surface.

Fig. 5. Bearing area curve of cylinder slot surface.

Fig. 6. Friction coefficient under dry condition test until.

Fig. 6. Friction coefficient under dry condition test until.

Fig. 7. Friction coefficient under lubrication condition.

Fig. 7. Friction coefficient under lubrication condition.

Fig. 8. EDS measurement result of surface component.

Fig. 8. EDS measurement result of surface component.

Fig. 9. Wear mechanism of oxide layer in (a) broaching, (b) grinding and lapping.

Fig. 9. Wear mechanism of oxide layer in (a) broaching, (b) grinding and lapping.

Fig. 10. Wear rate of specimen under lubrication and dry condition test.

Fig. 10. Wear rate of specimen under lubrication and dry condition test.

Fig. 11. Cross section images of wear tracks of specimen under.

Fig. 11. Cross section images of wear tracks of specimen under.

Fig. 12. Contact area characteristics.

Fig. 12. Contact area characteristics.

Table 1. Friction test conditions

Table 1. Friction test conditions

Table 2. Properties of cylinder slot surface

Table 2. Properties of cylinder slot surface