|Techmetals provides industrial hard chrome, salvage plating technology, quality, service, and cost advantages to manufacturers. Capacities include hard chrome plating on small parts, automatics, manual lines that support parts up to 10,000 pounds to exact specifications. We provide the same attention to detail for one part or thousands. Some areas have up to 40,000 lb. capacities and ceiling heights of 67′.Since Techmetals has a long history of experience and tooling background, we have helped to develop masking techniques. This eliminated costly plating splash-over on machine surfaces not requiring hard chrome. We’ve also developed salvage hard chrome plating methods that are more readily ground and deposit at extremely quick rates. These accomplishments enable us to provide our customers with the best possible service at the lowest overall cost – Ask our engineers about Hard Chrome alternatives!Techmetals processes Industrial Hard Chrome plating on exotic materials for the Aerospace, Oil & Gas, Automotive, Nuclear, Power Generation, Medical, Defense, Agriculture. Other industries include those which require us to have internal controls, testing, and third party testing.
Special production facilities automatically polish hard chrome plated tubes and hydraulic rods.
Standard Industry Specifications
QQ-C-320 B, AMS-2406, AMS-2460, MIL-DTL-23422, MIL-C-23422, ASTM B-177, MIL-STD 1501 F, and MPR 1059
We also run to customer specifications and have OEM and end customer approvals.
Hard Chrome Engineered & Performance Coatings
TM 105 is a dense, hard, wear-resistant chromium coating. The coating is used on all ferrous and many non-ferrous metals. Micro –cracked chrome coating is best known for greater hardness. It ranges from 68 to 72 Rockwell C, compared to 62-66 Rockwell-C for Standard Chrome. TM105 usually has better lubricity and is more resistant to wear or galling than most standard hard chrome applications.
TM 107 is a chromium metallic coating that exhibits excellent wear resistance, and can be used on all ferrous and non-ferrous metals.
TM 119 is a dense, hard, wear-resistant metallic coating used in applications that require optimum efficiency of or release in sliding wear or added release infused with a polymer matrix and Teflon like polymers.
TM 111 is a co-deposited metallic coating used on all ferrous and non-ferrous metals. This nickel – chrome or nickel phosphorous—chrome duplex coating is designed for superior wear and corrosion resistance type applications. This process uses the advantages of both coatings and solves the problems where either coating on their own may fail.
TM-Rx Medical Grade Chromium Coating
Industrial Hard Chrome Plating
Large Capacities, Automatics, and multiple shifts
Automatics to handle large volume jobs
Manual line for low quantities and job-shop type work
Thin Dense Chrome Plating
Techmetals Thin Dense Chrome offers superior wear resistance pound for pound at the thickness that it can be applied versus standard and micro-cracked chrome. One of the limitations is that thin dense chrome can only be applied .0001 to .0002. However, it is being surpassed by Techmetals Techcoat-400 which goes on around 1,800 Hv. This is off the standard Rockwell-C scale. Standard thin dense chrome is around 1100 Hv. Both thin dense chromium and Techmetals TechCoat-400 minimize dimensional changes.
Thin dense chrome plating is more of a matte finish and lacks a micro-cracked pattern. It offers some corrosion protection. It is a great coating for high loading and anti-galling.
Thin Dense Chrome has around 100,000 to 125,000 psi bond strength. (TechCoat-400 exceeds this as well.)
Thin Dense Chrome greatly reduces hydrogen embrittlement. (Techcoat-400 does not create hydrogen at the surface of a part that would create hydrogen embrittlement; however, it does process at a higher temperature)
Contact an account Manager at Techmetals to see what coating is best for you.
|Armatech is one of Techmetals latest advancements in coating technology. This hybrid version of TM 107 is a very hard coating that provides exceptional wear & corrosion resistance. One distinct characteristic of ARMATECH is the deposit conforms to the base metal. Edge build-up is virtually eliminated. Thickness is typically .0001″-.0003″. Although it may be varied slightly outside of these parameters to meet your needs . It is a hybrid version of standard thin dense chrome with different catalysis and specific controls on the power supply to provide this finish.
Performance Coatings to find some hard chrome replacement technologies like:
Diamonize, TM Invinc-alloy, Armakoat, TM TechCoat-400, DLA Diamond Like Alloys, and others.
Grinding & Honing Capabilities: Grind-Chrome-Grind One Stop Shop
Techmetals also has both horizontal and large vertical in-house grinding capabilities. We also team up with local grinding facilities to help be a one stop shop for grind-chrome-grind type applications.
Basics on Industrial Hard Chrome Plating and Engineering Properties
Chromium is a greyish-white metal, very hard and brittle and capable of being finished to a very high luster. Generally, hard chrome coatings are obtained from the electrolysis of chromic acid solutions from which the basic material for the process is chrome iron ore. The standard on most conventional hard chrome plating baths contains two main constituents, chromic acid and sulfuric acid. By varying these two constituents or by substituting the sulfuric acid, one is able to produce different types of hard chrome deposits. See the sketch below to understand the principle in hard chrome plating.
As deposited hard chrome coatings can be classified in two different classes. The two major applications are decorative chrome and industrial hard chrome; both are basically applied the same way, and exhibit some of the same properties. The following articles and tables will be solely based on industrial hard chrome.
Hard chrome coatings as applied are used to provide wear resistance, low coefficient of friction, anti-galling, mild corrosion resistance, and anti-sticking properties in plastic molds. The properties and characteristics makes the coating very versatile and uniquely qualified for many applications. In the following sections we will be expanding on its engineering, mechanical and physical properties.
Structure, Tribology and Performance
The electrodeposition of chromium is made up of a fine crystal structure. In very thin deposits below 0.1 mil, which chromium is very frequently plated, highly porous deposits are obtained, as in the case with many other electrolytic deposits. As the coating thickness grows, a gradual, progressive growth of the pores takes place. The chromium deposits’ cracks grow irregularly perpendicular to the substrate in all directions, so that the deposit is permeated by a fine network of cracks running at right angles to the surface.
All Chrome is Not Equal and each type of deposit might fit an application better than the other
This cracked deposit is gradually covered with more chromium but each successive layer cracks again. Finally, a series of net-like cracked deposits is formed, one over the other. Although even in comparatively thick coatings the individual cracks no longer penetrate the entire thickness of the coating down to the substrate, pores which go right through are present as a result of the continuously crisscrossing cracks.
While normal microscopic examinations do not reveal the crystal structure of the deposit, it does reveal that the deposit has a crack network. These cracks have no relationship to the crystal structure. The small body-centered cubic crystals with variable proportions of hexagonal crystals can only be seen by X-Ray methods.
Bright deposited chromium coatings generally have the finest grain patterns which exhibit preferential crystal orientation parallel to the surface. They possess a very pronounced crack network and contain many inclusions. Therefore, they have appreciably poorer corrosion resistance than matte appearing coatings which have largely un-oriented grains and contain as a rule very few cracks and inclusions. Many cracks in chromium coatings often originate from defects in the substrate which can continue through to the surface of the chromium. For more on this, see defect section on hard chrome.
Mechanical properties of Standard Hard Chrome
During the plating process of hard chrome, hydrogen is liberated at the part and some of the hydrogen gas is occluded in the deposit as well as the basis metal. This condition forms a hexagonal hydride which in turn has a higher absorption capacity for hydrogen due to its structure.
Since the surface of the chromium metal also has a tendency to absorb oxygen, it blocks the natural liberation of the hydrogen. Fortunately, it was found that if a plated part is heated slowly to a temperature of 400°F almost half of the occluded hydrogen was driven off. By raising the temperature of 750°F the coating became almost hydrogen free. These facts became the basis for the standard low-temperature heat treat of 375°F for 2 to 3 hours on many hard chrome plated parts.
Contrary to widely held opinion, the hydrogen content has no appreciable influences on the hardness of the chrome coating, and only cause a slight increase in hardness due to the cracking of the chrome layers during heat treatment.
Since the adhesion of chromium on the substrate is very high, the question of stress in the base metal is very important, particularly in the aircraft industry and for parts that are made of steels that are severely work hardened during the machining operations. To help eliminate some stress problems prior to plating, it is helpful to have them stress relieved at 400°F for one- half hour; especially, parts that have been ground prior to plating.
The internal stresses in the base metal produced by hydrogen absorption can affect not only the chrome coating but the occluded hydrogen can cause failure of the part. These stresses will show up first as compressive stress, which can be relieved by the 400°F heat treatment after plating. Since hard chrome coatings are highly tensile they exhibit a very high tensile stress which is a characteristic of the coating. These have been measured as high as 1350 kp/rnm 2 at chromium thickness of 2.0 mil to a more normal reading of 240 kp/rnm 2.
A substantial reduction of internal stresses can be achieved by subsequent heat treatment. This is not necessary in the case of the thin bright deposits which are permeated with cracks. On the other hand, heat treatment is often mandatory with thicker hard chromium deposits in order to reduce the stress to acceptable limits for practical use.
Physical Properties of Standard Hard Chrome
When hard chrome was originally used it was very thin and very porous, leaving a somewhat inferior coating. As the technology and chemistry of chromium was more fully understood it progressed as one of the most desirable coatings engineers recommended.
By varying the standard chromium bath (32 oz./gal. chrome with 32 oz./gal. of sulfuric acid), one is able to produce a varied type of deposit. During the process the plater may change his operating temperature, cathode to anode relation and tank concentrations all at once or one at a time to enable them to offer different types of chromium deposits. The following table is basically a list of the common properties of a hard chromium coating.
PROFILE: ELECTRODEPOSITED CHROMIUM
HARDNESS AND RESISTANCE TO WEAR
The special structure of electrodeposited chromium is responsible for the very high hardness of the coating. The hardest chromium coatings attain the hardness of corundum. They are twice as hard as other metals such as iron, cobalt and nickel. They are much harder than nitrated or case-hardened steel. An average figure obtainable is 800 to 100 Brinnel which is equivalent to 68-72 Rockwell C.
The hardness of chromium deposits are frequently given variable values. This is mainly due to the hardness being greatly affected by the conditions of the coating. This fact is generally recognized and therefore is taken into account in hardness measurements.
A quite common error often encountered is to use the hardness value of a deposit as a direct indication of its resistance to abrasion, or its wear resistance. It should not be overlooked that not only the hardness, but also the ductility and elasticity of a coating are determining factors in its resistance to wear.
Thus, no conclusion can usually be drawn with regard to abrasion resistance from hardness measurements, nor conversely from abrasion figures on hardness. The coating thickness of the chromium has an influence on the life, and if abrasion resistance of surface is the first consideration, thickness should not be less than 0.5 mil thick.
COEFFICIENT OF FRICTION
A valuable property of the hard chrome coating is its low coefficient of friction. In particular, the coefficient for dry friction is the lowest of all metals. See the following chart for comparison of surfaces.
COEFFICIENTS OF FRICTION OF VARIOUS METAL SURFACES
All hard chrome coatings have the tendency to reduce the fatigue limit on coated parts. Some coatings can reduce their limit up to as much as 50. A reduction of the magnitude can affect the performance and life of a part under severe conditions.
This significant fall in the fatigue resistance of hard chrome coatings under some circumstances rules out hard chrome coatings in many instances, because it is not possible to select suitable operating conditions which will avoid this impairment of quality. This characteristic makes it necessary to consider all circumstances to avoid any difficulties.
The corrosion resistance of hard chrome to atmospheric corrosion depends on the formation of a very thin film of oxide which protects it from further oxidation. At high temperatures 1,000 F and even greater, an oxidation barrier forms and exhibits a high resistance of corrosion.
Oxidizing and reducing agents have little effect on hard chrome, and it resists corrosion from most chemicals. It is however, rapidly attacked by hydrochloric acid, and under certain conditions moderately by sulfuric and nitric acids. The chemical attack generally originates from the cracks in the coating.
It should be noted also that the poor wettability of the hard chrome coating has a favorable effect on its corrosion resistance. This means that the corroding liquid cannot readily enter the narrow cracks which penetrate through the coating. The corrosion resistances of chromium towards numerous chemical effects are a result of passivity, however, only of limited value in the case of electrodeposited hard chrome coatings due to the crack network. See the following charts for additional corrosion resistance.
Corrosion Resistance of Chromium
The following table is a general indication of the resistance of chromium to various corrosive agents. The corrosive resistance of chromium in actual use is affected by operating factors such as temperature, concentration, aeration and the presence of small amounts of other constituents in the corrosive medium so that the data in this table must be considered only as an approximation. For critical conditions it may be preferable to conduct tests in the actual solution in use and under the actual operating conditions.
|CORROSIVE AGENTS CHART
*DATA IS FOR 10% SOLUTIONS OF THE CHEMICAL IN WATER EXCEPT AS NOTED.
Recommended Plating Thicknesses
As has already been pointed out, corrosive attack on hard chrome coatings commences at the base of the crack network.
From many experiments and observations it has been deduced the following recommendations:
There is no doubt that final grinding of the hard chromium coating increases the number of cracks in the deposit. This is due to the force exerted by the occluded hydrogen when the temperature of the deposit rises due to the grinding operation. Thus, thicknesses for thickness, unground coatings have a greater corrosion resistance than ground coatings.
The scope of hard chrome coatings is vast and has daily new applications being made. In the early days only the salvage side of the process was the one normally accepted by engineers, as the only alternative was normally to scrap worn or miss-machined parts. However, it has gradually been realized that parts treated with hard chrome are not only as good as new, but often prove to have a longer running life than untreated new parts. Hard chrome coatings today are used world wide as a normal part of manufacturing, with each individual application standing on its own unique qualities.