Showing papers on "Liquation published in 1995"

Phase diagram of the system Al2O3-SiO2

Abstract: Phase diagrams of the system Al2O3 - SiO2 as presented in the domestic and foreign literature are analyzed. The congruent and incongruent states of mullite, liquation in the solid phase, and the structures of mullite and sillimanite are discussed.

Effect of pre-welding heat treatments on welding a two-phase Ni3Al alloy

Abstract: Autogenous gas-tungsten are welding was performed on a two-phase Ni 3 Al alloy. Plates 3 mm thick were cut from a cast ingot and were subjected to three pre-welding heat treatments (PWHT), namely as-cast, annealed at 1100 °C for 23 h (HT1) and HT1 plus 1120 °C/30 min/air cooled (HT2). The as-cast alloy was characterized by dendrites with many eutectic cells located at dendrite boundaries (DBs). The eutectic cells were destroyed by HT1. However, HT2 made no further changes to the microstructure. Analysis by energy-dispersive X-ray spectroscopy (EDX) revealed that the DBs of as-cast alloy were enriched with Zr. The Zr enrichment at DBs was increased further by HT1 and HT2. No crack visible to the unaided eye was found in either the fusion zone (FZ) or the heat-affected zone (HAZ) due to welding. The FZ consisted of columnar grains with a eutectic structure along the boundaries. The eutectic structure was enriched with Zr and contained many microcracks and some Zr-rich phases. Micro-solidification cracks were occasionally found along boundaries in FZ. The alloy was sensitive to liquidation cracks that occurred along DBs in the HAZ. While PWHT had no effect on the characteristics of the FZ, PWHT had a notable effect on the severity of liquation cracking. The average liquation crack numbers per 5 cm weldment were 12 for as-cast, 14 for HT1 and 17 for HT2. The role of Zr-inducing solidification cracks in FZ and liquation cracks in HAZ is discussed.

Alloy liquation furnace

Abstract: The utility model relates to a novel alloy liquation furnace used for liquating metal from alloy ash, which comprises a furnace body, a feeding opening, a discharge chute opening, a liquation chamber and a combustion chamber. A low partition wall is arranged in the furnace body, and the combustion chamber is arranged on one side of the liquation chamber. The utility model has the advantages of simple structure and low cost, the cost is 1/200 of that of a reverberatory furnace while the quantity of metal processed per year is more than 300 tons, and the recovery rate is more than 95%.

Effect of preheating on creep properties of substrates coated by low-pressure plasma spraying

Abstract: The effect of preheating on rupture properties of substrate coated by low pressure plasma spraying was investigated in this study. Creep-rupture specimens of Ni-base superalloy, Mar-M247 were coated after preheating at several temperature ranges. Especially, a relationship between preheating temperature and microstructures of sprayed substrates was discussed. The results are summarized as follows.(1) Creep properties of Mar-M247, as a substrate, coated with CoCrA1Y were kept at the level of as cast material when preheated at the range of 1073-1173 K in low pressure plasma spraying.(2) The substrates of specimen coated after preheated at the range of 1473-1573 K were severely damaged in rupture life, strain and reduction of area. It is considered that liquation induced by high preheating in low pressure plasma spraying should occur and grow on the solidification grain boundaries of substrate. Consequently, creep properties were deteriorated, because of opening the grain boundaries during cooling period.(3) The mechanism of liquation and opening on the grain boundaries was deduced as the following. At first, selective decomposition of tungsten carbide in complex carbides is brought by heat. Simultaneously, carbon is dissolved around the grain boundaries which is one of elements decreasing melting point. After spraying, cooling shrinkage makes opening of solidification grain boundaries.