JPH0143835B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a surface treatment method for imparting high-temperature oxidation resistance and high-temperature corrosion resistance to heat-resistant alloys used in turbines, blowers, boilers, etc. Industrial gas turbines that use petroleum, natural gas, or the like as fuel tend to have higher gas temperatures at the turbine inlet in order to improve their efficiency. Furthermore, with the recent worsening of fuel supply conditions, the fuels used are becoming more diverse, and the content of corrosive impurities such as sulfur (S), sodium (Na), and vanadium (V) tends to increase. As a result, so-called hot parts such as turbine blades and combustors exposed to these high-temperature gases are subject to extremely severe high-temperature oxidation and high-temperature corrosion. Conventionally, these hot parts have mainly been constructed of heat-resistant alloys, and turbine blades in particular have been made of Ni-based and Co-based alloys called superalloys.
These superalloys generally prioritize high-temperature strength, so they have the disadvantage of poor corrosion resistance and oxidation resistance. For this reason, attempts have been made to impart oxidation and corrosion resistance to these heat-resistant alloys.
As an example, various surface treatment methods using chemical methods and physical methods are used, but when considering the effects and processing costs, there is no definitive method for any of them. The present invention is proposed to solve the above problems. That is, in order to impart high-temperature oxidation resistance and high-temperature corrosion resistance to a heat-resistant alloy, the present invention provides a first layer of Cr, which is a corrosion-resistant material, on the surface of the base material.
After electroplating, a second layer of coating liquid containing corrosion-resistant materials such as Al and Si metals, alloys, or their compounds is applied by spraying, brushing, or other methods, and then thermal diffusion and penetration treatment is performed. It is characterized by: The processing method of the present invention has the characteristics shown in Table 1 when compared with conventional processing methods.

[Table] Next, the present invention will be specifically illustrated by examples. Udimet520 (19% Cr 12% Co 6%) is a superalloy commonly used in gas turbine hot parts.
(Mo 3%Ti 2%Al 1%FeNi-Bal) was processed in the following order. After cleaning the surface of the base material with an alkaline emulsion detergent, steam cleaning with a fluorocarbon solvent is performed. The surface of the base material is immersed in a plating bath containing chromic anhydride as the main component, and Cr is electroplated to a thickness of approximately 50μ. Thoroughly wash the plating layer surface with water. A slurry coating liquid in which Al and Si having a particle size of about 0.1 to 1 μm are dispersed in an organic solvent (alcohol, solvent naphtha) is applied to the surface of the plating layer by a spray method. Place the base material treated above in an electric furnace and
After keeping at 330°C (±5°C) for 20 minutes to evaporate and evaporate the solvent, keep at 330°C (±5°C) for 15 minutes and take out. Further, this base material was held at 1080° C. for 4 hours in a hydrogen furnace, and then cooled in the furnace and taken out. Further, in this step, a vacuum furnace may be used instead of a hydrogen furnace. Furthermore, in this example
An example of processing for Udimet520 is shown, but other than this
Ni-based alloys (e.g. Udimet520, Udimet710,
Incone1713, etc.) and Co-based alloys (e.g. X-45,
Mar-M302) and stainless steel (e.g.
An extremely excellent surface treatment layer was also obtained when treating SUS304, SUS321, SUS347, SUS310, etc.). As mentioned above, the surface of the surface treated layer obtained by applying the slurry coating liquid to the plating layer and performing the diffusion penetration treatment is extremely smooth, and the Al and Si in the coating layer sufficiently penetrate into the plating layer to prevent plating. The pores in the layer had completely disappeared, and the entire treated layer was homogenized. That is, the melting point of Al is 660°C, and therefore, it is thought that heat treatment melts it and penetrates into the pores, as well as smoothing the surface. Furthermore, by coating the Cr plating layer with Al/Si slurry and performing a diffusion and penetration treatment,
It was observed that at the same time as the CrAlSi alloy layer was formed, some of the Al and Si that had diffused into the plating layer reached the base material and also diffused into the base material. Table 2 shows the results of a fly ashes erosion resistance test, a corrosion resistance test, and a practical test using a gas turbine blade, which were conducted on treated layers prepared by the method of the present invention and the conventional method. The method of the present invention exhibited superior performance in the fly ashes erosion test and corrosion resistance test compared to the conventional method. Furthermore, in practical tests using gas turbine blades, the blades of the present invention tended to have less fuel ash adhesion. Furthermore, the material of the present invention exhibited extremely excellent adhesion without peeling or cracking even in a thermal shock test in which the material was held at 1100° C. for 15 minutes and placed in water at 20° C. five times.

【table】

Claims (1)

[Claims] 1 Electroplating Cr, a corrosion-resistant material, on the surface of the heat-resistant alloy, applying a coating liquid containing Al and Si on top of it, and then coating the plated/coated area with Al,
By applying Si thermal diffusion infiltration treatment, CrAlSi
A method for surface treatment of a heat-resistant alloy, characterized by forming an alloy layer to impart high-temperature oxidation resistance and high-temperature corrosion resistance.