Papers by Author: Rudy Irwan

Abstract: Surface characteristics of CZT wafers machined using wire sawing, free abrasives lapping and polishing and ultra-precision grinding were investigated. Wire sawing resulted in the removal of material in both ductile and brittle regimes, but both polishing and grinding led to a ductile removal. The grinding produced very smooth surfaces free of embeddings and scratches, which is thus considered to have better machinability than the free abrasive machining. The nanoindentation and nanoscratch on MCT wafers at nanometric scales resulted in considerable plastic deformation, but no fracture features. The hardness of the MCT wafer was 500 to 550 MPa, and the coefficient of friction was particularly high, ranging from 0.45 to 0.55.

Abstract: Nanoindenting and nanoscratching were used to investigate removal and fracture characteristics of cemented tungsten carbide (cWC). Nanoindentation results indicated that the elastic modulus and hardness of WC grains were significantly greater than those measured in cobalt binder rich regions, respectively. Few evidences of cracking or fracture were observed on the indented surfaces using both in-situ atomic force microscopy and scanning electron microscopy. However, the pop-in events were observed from indenting load-displacement curves and the corresponding acoustic emissions were detected, indicating the occurrences of brittle fracture. Nanoscratch results demonstrated that similar removal characteristics existed, but cracking was observed in both surface and subsurface of the scratched samples.

Abstract: The effect of microstructure of cemented tungsten carbide materials on their mechanical properties and wear characteristics was investigated using nanoindentation and nanoscratch methods. The results indicated that the variation in grain size insignificantly affected the hardness, elastic modulus and friction coefficient of the work materials, but considerably influenced their removal rates. The carbide with coarser grains exhibited a much higher removal rate was obtained during scratching.

Abstract: Nanoindentation was used to study the deformation and removal mechanisms of cemented tungsten carbide. It was found that the microstructure of the material has significant influences on its mechanical properties, which determines the critical conditions for damage-free nanogrinding. The results also indicated that when material removal events occur at nanometric scale, such influences should be taken into account for gaining the full potential of nanogrinding.