Study on Surface Durability of Powder-Forged Rollers with Case-Hardening

Powder forging (P/F), which combines powder metallurgy (P/M) and forging technologies, leads to refined poreless microstructure in the material. Therefore, the mechanical property of the P/F material can be greatly improved comparing with that of the sintered material. In this paper, the rolling contact fatigue tests were conducted using a two-cylinder testing machine, and the surface failure and durability of the case-hardened P/F rollers were compared with those of the case-hardened conventional steel rollers. From the experimental and analytical results, it could be concluded that the failure mode of the P/F and the steel rollers was mainly spalling, and the surface durability of the P/F rollers was almost the same as that of the steel rollers. Evaluating the rolling contact fatigue life by the amplitude of the ratio of orthogonal shear stress τ _yz to Vickers hardness Hv, considering the case that every hardness distribution is the same to each other, the fatigue life of the Ni rich P/F roller was rather longer than that of the steel ones. The P/F process effectively improves the microstructure of the P/M material and makes the surface durability of the P/F material with high content of Ni approach to the level of steel. The P/F process was a good method to improve the mechanical properties of the sintered materials.