Production of component parts by metal injection moulding (mim)

Abstract

The invention relates to a method for producing component parts with a high degree of dimensional precision, made of NiTi-shape memory alloys. The invention makes it possible to apply a known metal injection moulding method to NiTi-shape memory alloys by adapting the binding system, temperature control and reducing the time necessary for debinding.

Description

[0001] The invention relates to a method of producing component parts, especially a method for producing component parts to near final dimensions with the aid of metal injection molding.STATE OF THE ART[0002] Metal injection molding (MIM=Metal Powder Injection Molding), also called metal powder injection, is known for a method of mass producing metallic component parts, especially for the manufacture of such component parts to near final contours (NNS=near net shape) R. M. German, A Bose (editors): "Injection Molding of Metals and Ceramics", New Jersey, Metal Powder Industries Federation MPIF (1997)).[0003] The MIM process allows small to middle size complex shaped parts to be produced in large numbers in an economical and automated manner. The MIM process supplies component parts with a density of 95 to 98% of the theoretical density and which with subsequent hot isostatic pressing can produce bodies (without encapsulating material) with a density of 100%.[0004] The method encompas...

AI Technical Summary

Benefits of technology

The invention is a method for making pre-shaped components of prealloyed NiTi powder using a two-component binder system. The method involves mixing the powder with a thermoplastic binder, injecting it into a mold, and then subjecting it to a thermal binding process. The resulting component part is then sintered. The use of a two-component binder system allows for better control over the flow characteristics of the feed stock and ensures a smooth transition to the finished component part. The method also allows for the recycling of the starting material without any loss of quality. The use of a thermoplastic binder system with good wettability and elastic properties helps to prevent cracking during the sintering process. The method is efficient and cost-effective, with the ability to produce complex shapes with good shape memory properties.

Problems solved by technology

The shape was conventionally imparted by the mechanical machining of castings of NiTi material made by melt metallurgy and the method has been limited in that the alloys in the martensitic state have a high yield strength and thus a poor machinability.

As a consequence the after-machining of melt metallurgy fabricated component parts has been possible only with a high expenditure of time and a high degree of tool wear.

The use of the metal injection molding process also for NiTi shape memory alloys has been a problem since apart from economical production rates, all of the small impurity contents required in the end product for the shape memory properties had to be insured.

The difficulties of fabricating NiTi component parts by metal injection molding (MIM) is that the contents of oxygen and carbon must be held as low as possible.

High impurity contents give rise to a reduced sintering activity of the metal powder and diminish the properties of the material in the sintered component part (for example by embrittlement).

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