Disclosed is a sintered NdFeB magnet having high coercivity (H.sub.cJ) a high maximum energy product ((BH).sub.max) and a high squareness ratio (SQ) even when the sintered magnet has a thickness of 5 mm or more. The sintered NdFeB magnet is produced by diffusing Dy and/or Tb in grain boundaries in a base material of the sintered NdFeB magnet by a grain boundary diffusion process. The sintered NdFeB magnet is characterized in that the amount of rare earth in a metallic state in the base material is between 12.7 and 16.0% in atomic ratio, a rare earth-rich phase continues from the surface of the base material to a depth of 2.5 mm from the surface at the grain boundaries of the base material, and the grain boundaries in which R.sub.H has been diffused by the grain boundary diffusion process reach a depth of 2.5 mm from the surface.

Disclosed is a sintered NdFeB magnet having high coercivity (H.sub.cJ) a high maximum energy product ((BH).sub.max) and a high squareness ratio (SQ) even when the sintered magnet has a thickness of 5 mm or more. The sintered NdFeB magnet is produced by diffusing Dy and/or Tb in grain boundaries in a base material of the sintered NdFeB magnet by a grain boundary diffusion process. The sintered NdFeB magnet is characterized in that the amount of rare earth in a metallic state in the base material is between 12.7 and 16.0% in atomic ratio, a rare earth-rich phase continues from the surface of the base material to a depth of 2.5 mm from the surface at the grain boundaries of the base material, and the grain boundaries in which R.sub.H has been diffused by the grain boundary diffusion process reach a depth of 2.5 mm from the surface.

Disclosed is a sintered NdFeB magnet having high coercivity (H.sub.cJ) a high maximum energy product ((BH).sub.max) and a high squareness ratio (SQ) even when the sintered magnet has a thickness of 5 mm or more. The sintered NdFeB magnet is produced by diffusing Dy and/or Tb in grain boundaries in a base material of the sintered NdFeB magnet by a grain boundary diffusion process. The sintered NdFeB magnet is characterized in that the amount of rare earth in a metallic state in the base material is between 12.7 and 16.0% in atomic ratio, a rare earth-rich phase continues from the surface of the base material to a depth of 2.5 mm from the surface at the grain boundaries of the base material, and the grain boundaries in which R.sub.H has been diffused by the grain boundary diffusion process reach a depth of 2.5 mm from the surface.

A chain component which has a simple surface treatment structure and in which satisfactory wear resistance is maintained for a long term; and a chain which employs this chain component so that a satisfactory wear elongation resistance is maintained are provided. A roller chain serving as an industrial chain for power transmission is constructed such that a pair of outer plates linked by two pins and a pair of inner plates linked together by two bushes onto each of which a roller is fit are alternately linked together in a plurality in a state that each pin is loosely fit in each bush. A chromium nitride layer is formed on the outer side of the steel-based substrate of the pin. The chromium nitride layer contains iron at a content higher than 0 mass % and lower than or equal to 55 mass %.

A cutting tool comprises a base including a hard alloy and a coating layer located on a surface of the base, wherein the coating layer comprises at least one TiCN layer, an Al.sub.2O.sub.3 layer and an outermost layer which are laminated in order from a side of the base, and a content of Cl at a thickness-center position of the TiCN layer is higher than a content of Cl at a thickness-center position of the outermost layer and the content of Cl at the thickness-center position of the outermost layer is higher than a content of Cl at a thickness-center position of the Al.sub.2O.sub.3 layer in a glow-discharge emission spectrometry (GDS analysis).