Microstructure and phase evolution in laser rapid forming of a functionally graded Ti–Rene88DT alloy

Wang

et al. 2016

Metals

Abstract:The damaged K465 nickel-based superalloy parts were repaired by laser forming repair technology. The cracking characteristics and grain boundary liquation in heat affected zones were investigated by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that the cracks originated from the heat-affected zone and extended to the repaired zone. The calculation by Thermol-Cale software showed that the larger γ 1 particles at grain boundaries partly dissolved in the γ phase, which made the solutes' concentration at the γ 1 /γ interface meet the eutectic-type liquation reaction condition of γ + γ 1 Ñ L. Then, grain boundaries liquation occurred and liquid films appeared with the temperature increasing in a rapid heating process. However, the intragranular γ 1 phase completely dissolved into the γ phase with no devotion to the liquid film. The dissolution of M 5 B 3 borides at grain boundaries could promote grain boundary liquation.

Section: Introductionmentioning

confidence: 99%

Research on the Grain Boundary Liquation Mechanism in Heat Affected Zones of Laser Forming Repaired K465 Nickel-Based Superalloy

Wang

et al. 2016

Metals

“…They also investigated the influence of compositional changes on microstructural changes in these alloys. Lately, Lin and Yue [18] have fabricated a graded material of TiRene88DT alloy using LRF. It was found that along the compositional gradient, a series of complex phase evolutions occurred.…”

Section: Since the Inception Of Japan's Functional Gradedmentioning

confidence: 99%

“…[7][8][9][10][11][12][13][14][15][16][17][18] In the study of the capabilities of LRF for the fabrication of FGMs, Li [5] studied the influences of processing parameters on the forming characteristics of 316L stainless and nickel-base alloys. On the other hand, Griffith [10] and Lewis [11] developed precise multiple-powder feeding capabilities for the LENS and DLF processes, respectively.…”

Section: Since the Inception Of Japan's Functional Gradedmentioning

confidence: 99%

Solidification Behavior and the Evolution of Phase in Laser Rapid Forming of Graded Ti6Al4V-Rene88DT Alloy

Yue

Yang

et al. 2007

Metall Mater Trans A

Self Cite

The graded material of Ti6Al4V-Rene88DT superalloy, which has shown the potential to be applied in aeroengines, was fabricated from prealloyed metal powders using the technique of laser rapid forming (LRF). A compositional gradient, from 100 pct Ti6Al4V to Ti6Al4V-38 pct Rene88DT, was achieved within a thickness of laser deposit of 54 mm. The solidification behavior and the phase evolution of the compositionally graded material were studied. The results of the X-ray diffraction (XRD) analysis together with the metallographic study showed that a series of phase evolutions, a + b fi a + b + Ti 2 Ni fi b + Ti 2 Ni, along the compositional gradient have occurred. The hardness value of the graded material was measured along the compositional gradient, and the results were explained in terms of the various phases present. The condition for columnar-to-equiaxed transition observed in the graded material was explained, based on Hunt's criterion. Finally, the morphology of b + Ti 2 Ni anomalous eutectic is discussed.

“…It is believed that the laser cladding of functionally graded material represents an improvement in technique over the traditional singlelayer method, which often causes problems of high dilution and weak coating interfaces. Indeed, graded coatings have been successfully applied to Al-, Ni-, and Ti-based substrates [9,10] and in the last decade, many studies on the laser cladding of functional gradient coatings were conducted on high-temperature materials that are used for applications in aircraft. [10] Unfortunately, similar work on magnesium alloys is still lacking.…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, graded coatings have been successfully applied to Al-, Ni-, and Ti-based substrates [9,10] and in the last decade, many studies on the laser cladding of functional gradient coatings were conducted on high-temperature materials that are used for applications in aircraft. [10] Unfortunately, similar work on magnesium alloys is still lacking. The main challenges of this research are to overcome the high chemical reactivity and the relatively low melting and boiling points of Mg alloys, and ultimately to produce defect-free coatings with good metallurgically bonded interfaces.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Phase Evolution in Laser Cladding of Ni/Cu/Al Multilayer on Magnesium Substrates

Yue

2009

Metall Mater Trans A

Self Cite

A multilayer coating of Ni/Cu/Al was fabricated on magnesium substrates using laser cladding. The solidification behavior and the phase evolution of the compositionally graded coating were studied. The results of the X-ray diffraction (XRD) analysis together with the metallographic study showed that a series of phase evolutions had occurred along the gradient (Mg) fi (Mg) + Al 12 Mg 17 fi (Mg) + Q + k 2 fi k 1 fi k 1 + c 1 fi c 1 + (Cu) + k 1 fi (Cu) + k 1 fi (Cu) fi (CuNi) fi (Ni). The rapid solidification condition had suppressed the invariant reactions that existed in the ternary Mg-Al-Cu alloy system. As a result, many of the predicted Al-rich brittle intermetallic compounds, which are detrimental to the performance of the coating, were not produced. The solidification path during the laser cladding of the Al and Cu layers was determined and the various phases, as predicted by the corresponding phase diagram, agreed well with the experimental results. Finally, the primary arm spacing (PAS) and the solidification morphology of the dendrites in the Cu and Ni layers were analyzed in relation to the solidification conditions.