| 摘要 |
PURPOSE:To form a superior boron layer at a lower temperature than usual, by closely sticking boron nitride on the material to be treated and diffusing boron decomposed by heating in nonoxidative atmosphere on the surface of the material to be treated. CONSTITUTION:The material to be treated 1 made of metals, such as Ti, Zr, Cr, Mo etc. or these alloys, is buried in the boron nitride powder 2 in the vessel 3 and the cover 4 is covered. The vessel 3 is put in the furnace core tube 5 and the temperature sensor 7 is maintained on the upper part of the cover 4. Vacuum degree of about 10<-6> Torr. is made by evacuating the inner part of the tube 5 by vacuum pump and temperature is raised slowly by the heater 6 and then, is maintained at 700 deg.C or more for about three hours. Boron nitride is decomposed into gaseous nitrogen and solid boron and nitrogen is discharged absorbing by the vacuum pump and then, boron is diffused and permeated in the inner part from the metal surface of the material 1. The material 1 is cooled to the room temperature in vacuum and is takne out from the furnace 5. Surface hardness of the material 1 is increased by the diffusion and permeation of boron and abrasion- resisting property is improved. Existence of chloride or fluoride having an inferior characteristic, is not recognized on the surface because chloride or floride is not used as reaction accelerator as usual. |
