Study On Hardfacing Materials Against Impact Abrasion

The wearable materials abroad are used among industry of metallurgy, mine, construction, coal, electric power, chemistry, farming machinery and military, most of which turn invalidation because of Abrasion. The level of foundational wearable materials made in china is appreciably lower than that made abroad. So the figure of economy loss due to abrasion is largeness. Grinding abrasion is the most important abrasion among kinds of wears, accounting for 50%. Based on incomplete statistics among industry of metallurgy, electric power, construction, coal and farming machinery, the expend of steel products due to grinding abrasion is more than 1 million ton,adding indirect loss because of replacing parts,the number of expending money is approximately 2-3 billion Yuan.High manganese steel is the first used material against abrasion. The weakness of high manganese steel in condition of low impact is not wearable by reason of insufficient work-hardening. Austenitic manganese steel exists the problem of low toughness and low security.In this paper, the author has successfully developed hardfacing alloys for impact abrasion and devised an impact hardening tester.Using the principle of energy conversion, we devised a drop hammer impact hardening tester in which hammer weights can be adjusted. After impact the abrasion test is carried out on the model of ML-100 wear tester. By these orderly-done experiments, the impact abrasion resistance of the hardfacing alloys is evaluated. The fundamental research on the effect of work-hardening and impact abrasion resistance of self-made coated metal electrodes is carried out according to the former experiments.Electrode covering is chosen as Fe-C-Mn-Cr alloys system, compounding the H08A type welding wire to do shielded-metal arc hardfacing. First, the influence of carbon, chromium and manganese in the coverings of the hardfacing electrodes on compositions, microstructures and properties of the build-up layers was investigated. Then, the comprehensive effect of the alloying elements on the microstructures and properties was studied by the orthonormal experiment so that the favorable directions for producing the suitable electrode can be obtained. It is necessary for graphite added to coverings. Suitable graphite addition is efficient to improve hardness and wear-resistant ability of hardfacing layers.When containing lower C, hardfacing layers give basically martensite and have better hardness and wear-resistant ability, but work-hardening effect being not obvious. But when containing C reaches to some point, hardfacing layers have common as-welded hardness and wear-resistant ability, but better work-hardening and resonable impacting wear resistance. So choosing the best containing C is very helpful to improve hardness, wear-resistant ability as welded, work-hardening effect and impacted wear-resistant ability.Along with the increase of containing Cr in hardfacing layers, as-welded hardness and wear-resistant ability vary in some degree. When containing Cr is lower, hardfacing layers exist basically austenite. Hardfacing layers have common as-welded hardness, but high work-hardening and impacting wear-resistance. But when containing Cr is over some amount, hardfacing layers have high as-welded hardness and work-hardening effect, but poor wear-resistant ability. So choosing the best containing Cr is very helpful to improve hardness, wear-resistant ability, work-hardening effect and impacting wear-resistant ability.Manganese-iron with middle carbon content has important influence on hardfacing layer hardness and wear-resistant ability. When containing lower Mn, hardfacing layers exist basically martensite and have high as-welded hardness and impacted hardness increase, poor work-hardening effect, poor wear-resistant ability. Along with containing Mn bit increasing, hardfacing layers have excellent as-welded hardness and impacted hardness increase, wear-resistant ability and work-hardening effect. When containing more Mn, hardfacing layers have low as-welded hardness, fine work-hardening effect and poor wear-resistant ability. So choosing the best containing Mn is very helpful to improve hardness and wear-resistant ability ,After impacting, there are a great deal of high density dislocation emerging in slid bands, which affects the slipping of crystals. So the hardfacing layers are strengthened by this behavior. There are much dislocation among austenite grains, and the tangle and anchoring of dislocation are increased in grain boundaries, which makes the dislocation movement and glide of crystals very difficulty. This is the reason that improves hardness and wear-resistant ability. The best assembled direction has excellent as-welded hardness, impacted hardness, hardness difference increased and impacted wear-resistant ability.As-welded hardness reaches HRC38.5, impacted hardness reaches HRC59, hardness difference reaches HRC20.5, the weight loss of abrasion is 49.3mg. Compared with high manganese steel, as-welded hardness increases 51%, impacted hardness increases 34% and wear-resistant ability increases 43%. In a word, this assembled direction of electrode has excellent work-hardening effect and wear-resistant ability, also can make up limitation of high manganese steel of low wear-resistant ability.