Method for heat treating cast titanium articles to improve their mechanical properties
AssigneeThe Garrett Corporation
InventorsDuane L. Ruckle, Ponciano P. Millan, Jr.
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Abstract
Cast titanium alloys and a method of heat treating the alloys in order to obtain fatigue and mechanical properties comparable to wrought titanium is disclosed. The heat treatment is practiced by solution heat treating a cast titanium article above its beta transus, rapidly cooling, stabilizing at a temperature within the alloy's alpha/beta phase range, and finally aging the article to achieve the desired properties.
Claims22
A method of heat treating a cast titanium alloy article comprising the steps of:
- heating the article to a temperature above its beta transus temperature;
- rapidly cooling the article to produce an acicular martensitic microstructure;
- thermally decomposing the martensitic microstructure by stabilizing the article at a temperature between 1500.degree.-825.degree. F.;
- and
- aging the article at a temperature of 1000.degree.-1300.degree. F. for a time of 1 to 8 hours.
An airfoil for use in a gas turbine engine or the like comprising a cast titanium alloy having a tensile strength of about 145 to 161 KSI produced by a method comprising the steps of:
- heat treating the airfoil to a temperature above its beta transus temperature;
- rapidly cooling the airfoil;
- stabilizing the airfoil at a temperature between 1500.degree.-1825.degree. F.;
- and
- aging the airfoil at a temperature of 1000.degree.-1300.degree. F. for a time of 1 to 8 hours.
An airfoil comprising:
- a cast titanium alloy having a tensile strength of about 145 to 161 KSI.
A method of heat treating a cast alpha/beta titanium alloy article comprising the steps of:
- transforming the alpha/beta microstructure of the article to a substantially beta microstructure by heating the article to a temperature above its beta transus temperature;
- converting the beta microstructure to a martensitic microstructure by rapidly quenching the article;
- stabilizing the martensite into alpha and beta platelets by heating the article to a temperature between 1500.degree.-1825.degree. F.;
- and
- decomposing a portion of the beta microstructure into an alpha/beta microstructure by aging the article.
A method of providing a hollow cast titanium alloy article comprising the steps of:
- casting a slightly oversized article around a leachable core within a mold by vacuum skull melting;
- removing the article from the mold;
- placing the article into a leaching agent to disintegrate the core;
- milling an oxygen enriched layer off the article;
- hot isostatically pressing the article;
- heat treating the article to a temperature above its beta transus temperature;
- rapidly cooling the article to produce an acicular martensitic microstructure;
- thermally decomposing the martensitic microstructure by stabilizing the article at a temperature between 1500.degree.-1825.degree. F.;
- and
- aging the article at a temperature of 1000.degree.-1300.degree. F. for a time of 1 to 8 hours.
A method of heat treating a cast titanium alloy article to relatively inexpensively provide the article with mechanical properties similar to those of a wrought titanium alloy article, said method comprising the steps of:
- heating the cast article;
- cooling the heated article to produce therein a acicular martensitic microstructure;
- stabilizing the cooled article at a first temperature in a manner casuing decomposition of the martensitic microstructure;
- and
- aging the stabilized article at a second temperature less than said first temperature.
Dependencies are inferred from the claim text.