Osamu Momose

The cyclic oxidation of Ni-20Cr alloys with small additions of cerium and silicon

The cyclic oxidation behaviour of Ni-20Cr, Ni-20Cr-1Si, Ni-20Cr-3Si, Ni-20Cr-0.3Ce, Ni-20Cr-1Si-0.3Ce and Ni-20Cr-3Si-0.3Ce alloys was studied in O 2 . Cyclic oxidation testing consisted of a 3.6 ks exposure at 1000 and 1100 o C followed by a minimum cooling period of 1.2 ks, during which the specimen temperature reached approximately 40 o C. This oxidation-cooling cycle was repeated up to five times. At 1000 o C, mass gains of the alloys increascd in the order of Ni-20Cr-1Si-0.3Ce<Ni-20Cr-0.3Ce <Ni-20Cr-3Si<Ni-20Cr-3Si-0.3Ce<Ni-20Cr-1Si<Ni-20Cr alloys, and surface oxides of Ni-20Cr, Ni-20Cr-1Si and Ni-20Cr-3Si alloys spalled at the oxide/alloy interface

Gas sulphonitriding steels in a CS2 and NH3 atmosphere

Abstract The structure and wear resistance of steels treated in a gas sulphonitriding atmosphere, which contained NH 3 and 0.006% CS 2 in endothermically derived propane carrier gas, was investigated. The sulphonitrided layers offer favourable wear resistance relative to untreated steels.

HIGH TEMPERATURE OXIDATION OF Ni-Cr ALLOYS

The oxidation behavior of Ni−20, −40, −60 and −80wt%Cr alloys was studied at 1373 and 1473K for 14.4ks in O 2 by thermogravimetric analysis, X-ray diffraction and scanning electron microscopy. The weight gain of the alloys increased with increasing time of oxidation. Increasing Cr content tended to increase the weight gain of the alloys. The spalling of surface oxide was observed at the oxide/alloy interface for all the alloys. The surface oxide for Ni-20Cr, Ni-40Cr and Ni-60Cr alloys spalled partially. On the other hand, the spalling of the surface oxide for Ni-80Cr alloy occurred over the entire surface. Oxide phases, morphology of surface oxide and oxidation kinetics will be presented.

Electroboronizing of titanium.

The titanium was treated electrolytically in a molten salt bath at current density is 200-600A/m2 in the temperature range of 1123-1223K for 10.8-54ks.It was confirmed by X-ray diffraction that the surface product was TiB2. The dual phase structures of a white layer and a black layer were observed on the cross section of treated specimen. The thickness of the boronized layer increased exponentially with treated temperature and parabolically with treated duration and decreased with icnreasing of current density. The maximum surface hardness was obtained treated at a current density 400A/m2.