Abstract: The invention provides a super hard and tough, nano-crystal austenite steel bulk material having an improved corrosion resistance, and its preparation process. The austenite steel bulk material comprises an aggregate of austenite nano-crystal grains containing 0.1 to 2.0% (by mass) of a solid solution type nitrogen, wherein an oxide, nitride, carbide or the like of a metal or semimetal exists as a crystal grain growth inhibitor between and/or in said nano-crystal grains. For preparation, fine powders of austenite steel-forming components, i.e., iron and chromium, nickel, manganese, carbon or the like are mixed with a substance that becomes a nitrogen source. Mechanical alloying (MA) is applied to the mixture, thereby preparing nano-crystal austenite steel powders having a high nitrogen concentration. Finally, the austenite steel powders are consolidated by sintering by means of spark plasma sintering, rolling or the like.

Abstract: The invention provides a super hard and tough, nano-crystal austenite steel bulk material having an improved corrosion resistance, and its preparation process. The austenite steel bulk material comprises an aggregate of austenite nano-crystal grains containing 0.1 to 2.0% (by mass) of a solid solution type nitrogen, wherein an oxide, nitride, carbide or the like of a metal or semimetal exists as a crystal grain growth inhibitor between and/or in said nano-crystal grains. For preparation, fine powders of austenite steel-forming components, i.e., iron and chromium, nickel, manganese, carbon or the like are mixed with a substance that becomes a nitrogen source. Mechanical alloying (MA) is applied to the mixture, thereby preparing nano-crystal austenite steel powders having a high nitrogen concentration. Finally, the austenite steel powders are consolidated by sintering by means of spark plasma sintering, rolling or the like.

Abstract: The invention provides a high hard, strength and tough nano-crystal metal bulk material and a preparation process thereof. The metal bulk material comprises an aggregate of metal nano-crystal grains, wherein an oxide, nitride, carbide, boride or the like of a metal or semimetal exists as a crystal grain growth inhibitor between and/or in the nano-crystal grains. The respective fine powders of nano-metal bulk material-forming components are mechanically alloyed (MA), using a ball mill or the like, thereby preparing nano-metal powders. Then, hot forming-by-sintering treatment such as spark plasma sintering, extrusion and rolling or explosive forming is applied to the powders to obtain a high hard, strength and tough nano-crystal metal bulk material.

Abstract: Proposed is a method for bonding of a ceramic body and a metallic body at a relatively low temperature not to cause substantial deformation or material degradation of the ceramic and metallic materials. The surface of the ceramic body is first irradiated with laser beams in vacuum so that the inorganic non-volatile constituent of the ceramic material, e.g. silicon when the ceramic is silicon nitride, is isolated on the surface of the ceramic body forming a layer. Thereafter, the metallic body is brought into contact with and pressed in vacuum against the thus laser beam-irradiated area of the ceramic body under an adequate pressing force and at an elevated but relatively low temperature which is, for example, not higher than 0.5Tm .degree.C., Tm .degree.C. being the melting point of the metallic material, so that the ceramic and metallic bodies are firmly bonded together.

Abstract: A spraying material is fed to and melted in a high energy density zone formed by converging a laser beam therein with a converging lens or a mirror, and the molten spraying material is rendered into particles by jetting a carrier gas stream such that the axis thereof crosses the axis of the laser beam in the high energy density zone to blow the particles of the molten spraying material against a base surface disposed to be normal to the carrier gas stream axis beyond the high energy density zone so as to form a film of the spraying material on the surface.

Abstract: The slag formed when concrete is melted by exposure to a laser beam, when caused to incorporate therein a MgO-rich supplementary material, loses it viscosity and, on cooling, refrains from expanding and, consequently, assumes a readily removable state. The slag thus set can be easily removed by allowing a cleaning device such as the rotary wire brush to pass along the part of concrete melted by the laser beam. In accordance with this method, the apparatus for cutting concrete can be readily applied to a remote control system and will manifest an outstanding effect in a highly hazardous site such as is involved in the dismantling of a biological shield wall of concrete in a nuclear reactor.