CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the United States national phase of International Application No. PCT/JP2018/037586 filed Oct. 9, 2018, and claims priority to Japanese Patent Application No. 2017-207885 filed Oct. 27, 2017, the disclosures of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to metal powder to be used in a rapid melt-quenching solidification process, such as a three-dimensional additive manufacturing method, a thermal spraying method, a laser coating method, and a surfacing method. The present invention more specifically relates to Fe-based alloy powder.

BACKGROUND ART

Three dimensional (3D) printers are used in manufacturing shaped metal articles. In these 3D printers, the shaped articles are manufactured by an additive manufacturing method. In the additive manufacturing method, spread metal powder is irradiated with a laser beam or an electron beam. This irradiation melts particles of the metal powder and the particles then solidify. Such particles are bonded to each other through the melting and the subsequent solidification. Irradiation is selectively applied to some portions of the metal powder. Unirradiated portions in the powder do not melt. Bonded layers can be formed only in the irradiated portions.

Additional metal powder is spread over the bonded layers. This metal powder is irradiated with a laser beam or an electron beam. This irradiation melts particles of the additional metal powder, and the particles then solidify. Such particles are bonded to each other through the melting and the subsequent solidification, and fresh bonded layers can be formed. The fresh bonded layers are also connected to the bonded layers formerly formed.

Repetition of the bonding by irradiation causes an aggregate of the bonding layers to gradually grow. Such stepwise growth produces a three-dimensional shaped article. A complicatedly shaped article can be readily produced by the additive manufacturing method. PTL 1 (JP4661842B) discloses an example additive manufacturing method.

Requirements for alloys used in structures for, for example, aircraft and space fields are high strength and high fatigue resistance. Maraging steel is suitable for such applications.

PTL 2 (JP2013-253277A) discloses maraging steel containing Fe, which is a main element, Ni, Co and Mo. The content of Co in the maraging steel is 7% by mass or more. The maraging steel also contains W. The maraging steel does not contain Ti.

PTL 3 (JP2008-185183A) discloses maraging steel containing Ni, Cr, Mo and Co. The maraging steel has undergone a nitriding treatment.

CITATION LIST

Patent Literatures

PTL 1: JP4661842B

PTL 2: JP2013-253277A

PTL 3: JP2008-185183A

SUMMARY OF INVENTION

In an additive manufacturing method, a metal material is rapidly melted and then quenched to solidify. Conventional maraging steel is not suitable for metal powder used in processes involving such rapid melt-quenching solidification. An Fe-based alloy has been demanded that is suitable for the additive manufacturing method and that can provide a shaped article having superior mechanical properties. Such an alloy is also useful in, for example, a thermal spraying method, a laser coating method, and a surfacing method.

An object of the present invention is to provide an Fe-based metal powder that is suitable for a process involving rapid melt-quenching solidification, and that can provide a shaped article having superior properties.

The present invention provides the following items:

[Item 1]

An Fe-based metal powder for shaping, wherein the Fe-based metal powder is made of an Fe-based alloy, comprising:Ni in an amount of 15.0% to 21.0% by mass;Co in an amount of 0% to 10.0% by mass;Mo in an amount of 0% to 7.0% by mass;Ti in an amount of 0.1% to 6.0% by mass;Al in an amount of 0.1% to 3.0% by mass; and

the balance being Fe and incidental impurities.

[Item 2]

The Fe-based metal powder according to item 1, wherein the amount of Co in the Fe-based alloy is 0.5% by mass or less.

[Item 3]

The Fe-based metal powder according to item 1, wherein the amount of Co in the Fe-based alloy is 0.5% to 10.0% by mass.

[Item 4]

The Fe-based metal powder according to any one of items 1 to 3, wherein D50/TD is 0.2 to 20, the D50/TD being a ratio of a mean particle diameter D50 (μm) of the metal powder to a tap density TD (Mg/m3) of the metal powder.

[Item 5]

A method of producing a shaped article using a raw Fe-based metal powder, comprising the steps of:(1) providing Fe-based metal powder made of Fe-based alloy containing:Ni in an amount of 15.0% to 21.0% by mass;Co in an amount of 0% to 10.0% by mass;Mo in an amount of 0% to 7.0% by mass;Ti in an amount of 0.1% to 6.0% by mass;Al in an amount of 0.1% to 3.0% by mass; andthe balance being Fe and incidental impurities, and(2) melting and then solidifying the Fe-based metal powder to produce a non-heated shaped article.
[Item 6]

The method according to item 5, wherein the non-heated shaped article has a Rockwell hardness of 30 to 40.

[Item 7]

The method according to item 5 or 6, further comprising, subsequent to step (2), the step of:(3) heating the non-heated shaped article to produce a shaped article.
[Item 8]

The method according to item 7, wherein step (3) comprises the substeps of:(3-1) solutionizing the non-heated shaped article; and(3-2) aging the solutionized shaped article.
[Item 9]

The method according to claim8, wherein substep (3-1) is performed at a temperature of 700 to 900° C. for a period of 1.0 to 3.0 hours, and substep (3-2) is performed at a temperature of 450 to 550° C. for a period of 3.0 to 6.0 hours.

[Item 10]

The method according to any one of items 7 to 9, wherein the shaped article after step (3) has a Rockwell hardness of 50 to 60.

[Item 11]

The method according to any one of items 7 to 10, wherein the shaped article after step (3) satisfies the following expressions (I) and (II):
1.5≤(ATH/ATR)×(CTH/CTR)≤3.5  (I), and
1.5≤(BTH/BTR)×(CTH/CTR)≤3.5  (II),
where, ATHrepresents tensile strength at 400° C., ATRrepresents tensile strength at 25° C., BTHrepresents 0.2% proof stress at 400° C., BTRrepresents 0.2% proof stress at 25° C., CTHrepresents elongation at break at 400° C., and CTRrepresents elongation at break at 25° C.

A shaped article having superior properties can be produced from an Fe-based metal powder according to the present invention through a process involving rapid melt-quenching solidification.

