Tribological Properties of Aluminum Alloy treated by Fine Particle Peening/DLC Hybrid Surface Modification

In order to improve the adhesiveness of the DLC coating, Fine Particle Peening (FPP) treatment was employed as pre-treatment of the DLC coating process. FPP treatment was performed using SiC shot particles, and then AA6061-T6 aluminum alloy was DLC-coated. A SiC-rich layer was formed around the surface of the aluminum alloy by the FPP treatment because small chips of shot particles were embedded into the substrate surface. Reciprocating sliding tests were conducted to measure the friction coefficients. While the DLC coated specimen without FPP treatment showed a sudden increase in friction coefficient at the early stage of the wear cycles, the FPP/DLC hybrid treated specimen maintained a low friction coefficient value during the test period. Further investigation revealed that the tribological properties of the substrate after the DLC coating were improved with an increase in the amount of Si at the surface

Tribological Properties of Aluminum Alloy treated by Fine Particle Peening/DLC Hybrid Surface Modification

In order to improve the adhesiveness of the DLC coating, Fine Particle Peening (FPP) treatment was employed as pre-treatment of the DLC coating process. FPP treatment was performed using SiC shot particles, and then AA6061-T6 aluminum alloy was DLC-coated. A SiC-rich layer was formed around the surface of the aluminum alloy by the FPP treatment because small chips of shot particles were embedded into the substrate surface. Reciprocating sliding tests were conducted to measure the friction coefficients. While the DLC coated specimen without FPP treatment showed a sudden increase in friction coefficient at the early stage of the wear cycles, the FPP/DLC hybrid treated specimen maintained a low friction coefficient value during the test period. Further investigation revealed that the tribological properties of the substrate after the DLC coating were improved with an increase in the amount of Si at the surface

A new fracture mechanics model for multiple matrix cracks of SiC fiber reinforced brittle-matrix composites

A new model is proposed for multiple matrix cracking in order to take into account the role of matrix-rich regions in the cross section in initiating crack growth. The model is used to predict the matrix cracking stress and the total number of matrix cracks. The model converts the matrix-rich regions into equivalent penny shape crack sizes and predicts the matrix cracking stress with a fracture mechanics crack-bridging model. The estimated distribution of matrix cracking stresses is used as statistical input to predict the number of matrix cracks. The results show good agreement with the experimental results by replica observations. Therefore, it is found that the matrix cracking behavior mainly depends on the distribution of matrix-rich regions in the composite. (C) 1999 Acta Metallurgica inc. Published by Elsevier Science Ltd. Ali rights reserved

Modification of surface properties on a nitride based coating films through mirror-quality finish grinding

In this study, we performed a specific precision grinding process in an attempt to improve the mirror-quality finish and tribological characteristics of titanium nitride based coating films (TiN, TiCN, and TiAIN). The ground surfaces were highly smooth with no evidence of cracking, chipping, or peeling, demonstrating that the hard coating films were finished uniformly. For the TiAIN coating, a significant high level mirror-quality finish was achieved with an average roughness Ra of 4 nm. In addition, for all films, the employed grinding process led to superior tribological characteristics. In the case of the TiN film, the precision grinding process produced a carbon- and copper-rich surface layer, as well as higher compressive residual stress