Nobuyasu Yokoi

Life improvement of TiN-duplex-treated tool steel by tempering

Effects of tempering the nitrided substrate on the life of TiN-duplex-treated tool steel are studied as a potential tool material for plasticity processes. Ring-on-block sliding tests are carried out against aluminum alloy without lubrication to evaluate the life of the TiN coating film under a high-load, low-speed condition where wear takes place predominantly. Results show that the tempering prolongs the TiN coating film life more than twofold. This is due to an increased fracture toughness of the substrate and improved adhesive strength of the coating-substrate interface, both suppressing wear of the TiN layer by scratching.

Comparison of the feedback source between shaft displacement and load variation in controlled bearings

Abstract There has been much research into improving the characteristics of an externally pressurized thrust bearing and this has used two methods: a flow control device and sensing mechanisms. This report uses the latter method and deals with an externally pressurized thrust gas bearing which has a variable flow control device controlled by two signals. One source of signal is shaft displacement and the other is load variation. The results predict that a bearing controlled by load variation has a much higher performance than that controlled by shaft displacement. In the experiment a bearing which feeds back load variation showed a high performance for shaft displacement over a wide range of frequencies.