Coating for sintering hard alloy product

Abstract

The invention discloses a coating for sintering a hard alloy product, which comprises 14.7%-15.4% of high wear resistant C (carbon) powder, 8.4%-8.8% of coarse C powder, 6%-7.5% of Tween80, 2%-3% of normal butanol, 2.5%-5% of PEG (polyethylene glycol) 6000, 22%-25% of metal oxide powder and 37.5%-40% of deionized water, wherein the metal oxide powder includes titanium oxide powder, zirconium oxide powder or aluminum oxide powder, and the ratio of the high wear resistant C powder to the coarse C powder ranges from1.6:1 to 1.8:1. The coating is applicable to sintering of all low-weight hard alloy blanks with the weight less than 250g and cobalt content lower than or equal to 25%, the surface of a boat has no gathered particles after the coating is painted, the coating is not adhered to the boat in sintering, and the sintered product is free of carburization and decarburization and has no dent. Besides, the labor intensity of workers spraying the boat is reduced, dependence of final product quality on manual boat spraying quality is technically and greatly reduced, and the coating is economical.

Description

technical field [0001] The invention relates to a coating for sintering of hard alloy products, which is suitable for sintering hard alloy blanks with a cobalt content of ≤25%. Background technique [0002] During the sintering process of cemented carbide compacts, due to the existence of cobalt liquid phase and the small wetting angle between cobalt and graphite, cemented carbide products will bond with graphite boats, resulting in carburization and shrinkage deformation. In order to prevent this phenomenon, two methods are proposed: one is to use carbon paper on the boat, but the cost of commercially available anti-sticking and anti-carburization carbon paper is relatively high, and carbonized paper dust also pollutes the furnace and blocks the tube of the sintering furnace. The second is to use boat paint to separate the compact from the boat. Most of the commercially available paint is based on carbon materials, with the addition of metal oxides and other suspension disp...

AI Technical Summary

Problems solved by technology

In order to prevent this phenomenon, two methods are proposed: one is to use carbon paper on the boat, but the cost of commercially available anti-sticking and anti-carburization carbon paper is relatively high, and carbonized paper dust also pollutes the furnace and blocks the tube of the sintering furnace. The second is to use boat coating to separate the compact from the boat. Most of the commercially available coatings are mainly carbon materials, and metal oxides and other suspension dispersion system substances are added as auxiliary materials.

The Chinese patents "Vacuum Anti-sticking Coating for Cemented Carbide" (CN 101104773 A) and "A Coating for Cemented Carbide Production" (CN 1597885 A) have relatively low metal oxide content and are only suitable for low-cobalt hard alloys. Alloy sintering is not suitable for sintering products with a cobalt content of more than 13%, and the moisturizing component formaldehyde used in the latter design is harmful to the human body; the content of metal oxides in "High binder phase cemented carbide sintering coating" (CN 101928478 A) More than 55%, it can play a very good anti-sticking and anti-seepage effect on products with large unit weight, large size, high cobalt and wide tolerance range, but it is easy to cause delamination for products with small unit weight, high dimensional accuracy and narrow performance range. Carbon, dents; "Special coating for vacuum sintering of high-cobalt cemented carbide and its preparation and use method" (CN 101972848 A) and "a coating for sintering of high-cobalt cemented carbide products" (CN 101386055 A) both added Titanium dioxide, titanium dioxide can form an effective film layer, but it basically fails for products with a cobalt content greater than 15%. The thickness of the film layer is increased by adding carbon black with a content greater than 25%, but the content of decarburization titanium dioxide cannot reach Certain requirements will inevitably lead to carburization, and pure high-purity and high-wear-resistant carbon black is easy to break away from the boat and damage equipment; "a coating for hard alloy production" (CN 1482193 A) uses The composition reaches more than 33%, and no metal oxide is added. Small products with high cobalt are easy to carburize, and large products with high cobalt are sticky.

If the cobalt content is low, the sintered coating is mainly composed of carbon black without adding metal oxides; while for the high cobalt content, the coating without adding metal oxides will appear sticking boats, carburizing deformation, etc., and the content of metal oxides If it is low, it will stick to the boat, if it is high, it will be difficult to disperse and easy to agglomerate, and coating deposition and shelling will often occur. Brushing the surface of the boat can not avoid the existence of particles, and often cause product dents, especially for high-cobalt, large-diameter, and low-height products. , the concave waste rate is extremely high, and the coating operation requirements are very high

In addition, the high-cobalt and low-cobalt coatings have inconsistent formulations and brushing methods. In production, spraying is labor-intensive, and paint selection errors lead to sticking boats and scrapping.