Structural features of powder materials operating under high temperatures,stresses, and wear

It is known that parts of hot zones of metallurgical plants as well as heav ily loaded pressing and forging tools operate under a high temperature, ele vated mechanical stresses, the action of a steam ambient, slag, surface wea r due to contact with the hot metal, etc. The possibility of providing the requisite properties by using high-temperature alloys has already been exha usted because the complexity of their composition intensifies the segregati on inhomogeneity of the ingots which cannot be eliminated in the process of hot deformation and homogenizing annealing. As a rule, fracture starts und er the conditions of cyclic loads on local structural defects such as accum ulations of coarse particles of the eutectic gamma'-phase, borides, carbide s, nonmetallic inclusions. The chemical inhomogeneity and the structural de fects caused by it can be removed by using methods of powder metallurgy tha t can provide materials with unique properties unattainable in the conventi onal metallurgy. The present paper is devoted to the special features of th e structure of powder nickel alloys.