Particles having a sinterable core and a polymeric coating, use thereof, and additive manufacturing method using the same
Particles each having a sinterable core and a polymeric coating on at least a part of the core, wherein the polymeric coating includes a polymer that can be removed via decomposition by heat, catalytically or by solvent treatment, and wherein the polymeric coating is present in an amount of 0.10 to 3.00% by weight, relative to the total weight of the particles, as well as the use of these particles in an additive manufacturing process such as a powder bed and inkjet head 3D printing process. The particles and the process are able to provide a green part having improved strength and are thus suitable for the production of delicate structures which require a high green strength in order to minimize the risk of structural damage during green part handling.
1. A powder comprising particles, the particles each having a sinterable core and a polymeric coating on at least a part of the core,
wherein the polymeric coating comprises a polyvinyl pyrrolidone having a weight average molecular weight (Mw) of from 1,000-40,000 g/mol, and wherein the polymeric coating is present in an amount of 0.50 to 5.00% by weight, relative to the total weight of the particles.
2. The powder according to claim 1 , wherein the polymeric coating further comprises a surfactant.
3. The powder according to claim 1 , wherein the sinterable core is made of metal, metal alloy, ceramic or cermet.
4. The powder according to claim 1 , wherein the sinterable core is made of stainless steel.
5. The powder according to claim 1 , having a particle size distribution such that 95% by weight or more of the particles have a diameter of 50 μm or less (X95<50 μm).
6. The powder according to claim 1 , wherein the polymeric coating further comprises a nonionic surfactant.
7. The powder according to claim 1 , wherein the polymeric coating further comprises a wetting agent.
8. The powder according to claim 7 , wherein the wetting agent comprises a polyol.
9. The powder according to claim 1 , wherein the polymeric coating comprises at least 80% by weight of the polyvinyl pyrrolidone.
10. The powder according to claim 1 , wherein the polymeric coating comprises crosslinked polyvinyl pyrrolidone.
11. An additive manufacturing process, wherein the powder as defined in claim 1 are used in the additive manufacturing process.
12. The process according to claim 11 , wherein a liquid binder composition is used for preliminary binding of the particles, the liquid binder composition comprising polyvinyl pyrrolidone.
13. A green part obtainable by binding the particles of the powder as defined in claim 1 , with a binder composition.
14. The green part according to claim 13 , wherein the binder comprises polyvinyl pyrrolidone.
15. The green part according to claim 13 , which has a green strength of 2.7 MPa or more.
16. The green part according to claim 13 , which has a green strength of 3.0 MPa or more.
17. An additive manufacturing method, comprising a step of binding the particles of the powder as defined in claim 1 , with a binder composition to form a green part, a step of removing the binder composition and the polymeric coating by heat treatment, solvent extraction or catalytically to form a brown part, and a step of sintering the brown part to obtain an object made from a material of the core of the particles.
18. Additive manufacturing method according to claim 17 , which is a powder bed and inkjet head 3D printing method.