Dynamically Impacting Method for Simultaneously Peening and Film-forming on Substrate as Bombarded by metallic Glass Particles

Abstract

A dynamically impacting method comprising simultaneously peening a substrate surface and forming a thin film of metallic glass on the substrate surface for increasing the surface hardness, fatigue resistance, anti-fracture toughness and corrosion resistance of the substrate simultaneously.

Claims

1. A dynamically impacting method comprising: A. Preparation of metallic glass particles or liquid metal alloy particles; and B. Bombardment of the metallic glass particles or liquid metal alloy particles as driven by a compressed inert gas against a substrate to harden a surface of the substrate and to form a thin-film of metallic glass or liquid metal alloy for increasing corrosion resistance of the surface of the substrate.

2. A method according to claim 1, wherein said metallic glass particles are made by melting a metallic glass raw material in a vacuum furnace and then quickly cooled and atomized to form metallic glass particles.

3. A method according to claim 1, wherein said bombardment of metallic glass particles on the substrate comprises: a high-pressure bombardment bye bombarding metallic glass particles under a high pressure ranging from 5 bars through 15 bars to harden and smoothen the surface of said substrate; and a low-pressure bombardment by further bombarding the metallic glass particles under a low pressure ranging from 0.1 bars through 5 bars to rapidly superimposedly form thin films of metallic glass on said substrate to form corrosion resistance and polishing surface of said substrate.

4. A method according to claim 1, wherein said metallic glass particles as obtained from said vacuum furnace are collected and classified into a plurality of particle sizes for optional or selective uses.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is an illustration showing the dynamically impacting method as performed in the present invention.

[0007] FIG. 2 is a sectional illustration showing the surface treatment of a substrate in accordance pith the present invention.

DETAILED DESCRIPTION

[0008] In accordance with the present invention, particles of metallic glass or liquid metal alloy are provided for shot peening and film-forming on a substrate, preferably a metal substrate or an alloy substrate of a work piece or an engineering, structural object not limited in the present invention.

[0009] The process steps of the present invention comprises:

1. Preparation of Metallic Glass particles: [0010] A raw material of metallic glass or liquid metal alloy is prepared by adjusting a proper atomic percentage of the elements forming the metallic glass. [0011] The raw material of metallic glass is then put into a vacuum furnace for melting the metallic glass and then quickly cooled and atomized by an ultrasonic argon gas to produce metallic glass particles. [0012] The metallic glass particles are then collected and classified into several grades, for instance, a particle size of 510 microns, 1020 microns, 2050 microns, 50100 microns, and 100300 microns. The smaller the particle size is, the finer and denser the peened surface on the substrate will be.
2. Bombardment of the Metallic Glass particles on the substrate: [0013] The metallic glass particles 1 are bombarded against a surface of the substrate 2 as shown in FIG. 1. The metallic glass particles are ejected through a nozzle or gun 11 as driven by compressed inert gas including argon to dynamically bombard the substrate surface to harden and smoothen the corrugated or rough substrate surface. [0014] Substantially, the substrate 2 has its upper surface portion hardened to be a hardening zone 21 as shown in FIG. 2. Since the metallic glass particles 1 are continuously bombarded on the substrate surface, the above-mentioned corrugated or rough surface will then be smoothened by the further bombardment of metallic glass particles, thereby forming a metallic glass thin film 10 over the hardening zone 21 [0015] By so doing, the hardening zone 21 may increase the hardness, fatigue resistance and fracture toughness of the substrate, and the metallic glass thin film 10 may further increase the corrosion resistance of the substrate. Comparatively, this invention may increase the hardness and the corrosion resistance simultaneously, rather then the two-steps as disclosed in the prior art of U.S. Pat. No. 8,323,729 as early depicted in the Background of the Invention of the Specification. [0016] Critically, the bombardment of the metallic glass particles on the substrate may be further divided into two sub-steps, namely: [0017] A. High-Pressure Bombardment: [0018] The metallic glass particles are bombarded against the substrate surface at a speed of at least 10 meters/second as driven by compressed argon gas under a high pressure of 515 bars to harden and smoothen the substrate surface. [0019] B. Low-Pressure Bombardment: [0020] The metallic glass particles are further bombarded against the substrate surface under a low pressure of 0.15 bars to rapidly superimposedly form thin films of metallic glass on the substrate surface, thereby forming a corrosion resistant surface with polishing (smooth and shiny) appearance. [0021] Therefore, the finished surface of the substrate may have hardened zone 21 and metallic glass thin-film layer 10 for enhancing both hardness and corrosion resistances to be superior to the prior art. [0022] By bombarding metallic glass particles on a 6061 aluminum substrate, the surface hardness is 23.41 GPa (2212 Hv), which has been greatly increased in comparison with that untreated with metallic glass bombardment (only 1.13 GPa, 107 Hv). [0023] Meanwhile, after bombardment of the metallic glass particles on the high speed steel pitch mold surface, the hardness has been increased from 7.06 GPa (667 Hv) to 22.03 GPa (2082 Hv). Furthermore, it is not corroded (without forming oxide layer) after exposure to the air for 3 weeks.

[0024] The present invention has the following advantages superior to the prior art and the conventional shot peening: [0025] 1. The metallic glass particles may be formed as a true spherical shape to form a smooth polishing surface after bombardment. [0026] 2. The metallic glass particles have high anti-fracture strength, not easily broken to injure the processing surface and the particles may also be recycled for re-use. [0027] 3. The metallic glass has high hardness and density to thereby increase its dynamic energy when bombardment against the substrate to form a bombarded surface with increased hardness. [0028] 4. The metallic glass particles when impacted on the substrate will be partially melted due to frictional heat when impacting the substrate surface at high speed (such as 10 meters/second or even higher) to a temperature higher than its glass transition temperature (Tg) so as to form a thin film of metallic glass to be adhered on the substrate surface, which will be quickly cooled to a room temperature to still keep its amorphous property. It is very important since such a metallic glass thin film as formed on the substrate surface will render a better corrosion resistance of the substrate of the work piece or structural object. A production cost may then be greatly reduced.

[0029] Conclusively, without further treatment for corrosion resistance, the bombardment of the metallic glass particles on the substrate surface, it may render the substrate surface to be corrosion resistant in addition to the increasing of hardness, the fatigue resistance and the anti-fracture toughness.

[0030] The present invention may be further modified without departing from the spirit and scope of the present invention.